Congratulations and welcome! It looks like you have a real jewel there.
Don't worry about the ballast filling. It could be a bad seal on the valve (easy, inexpensive fix), or it is possible that you just did not have it closed all the way. The vent in the v-berth did not cause the problem. If you need to replace the the vent plug it is just a standard expanding transom plug that you can get anywhere boat accessories are sold.
You are 100% correct on the 5-year replacement cycle on sails. That's a racing thing and you (we)
dont have a racing boat. New sails are nice and they do make a (small) difference.
Spending a lot of money to try to make a Mac (particularly a motorsailer) sail faster reminds me of a friend who raced motorcycles. I was in his shop one day and he was showing me the new alloy wheels he had just purchased for an unconscionable price in order to shave 10 pounds or so off the weight of the bike. My (unspoken) opinion was that 10 pounds was not going to make much of a difference as long as he was not willing to shave the 40+ pounds he was carrying around his waist. He had a fundamental (no pun intended) problem that fancy wheels were not going to fix.
There are a lot of 20+ year Macs still on the original sails and the rest are probably still on the first replacement set. If they are worn out, replace them but otherwise just get out there and have fun.
I agree 100% with Russ on the maintenance items he mentioned. Since you don't have working sails you need to be sure that your engine is not going to let you down. I'll add:
Engine and Fuel
Replace the fuel filter in the engine (if it has one)
Make sure that the fuel line and the priming bulb are in good condition. The fuel line should not feel soft or mushy. The priming bulb should not feel stiff or hard.
It's not common but there may be a fuel filter between the tank and the engine. Replace it if you find one.
Check the connectors on the fuel line. Some have O-rings that may dry out. If that happens you may get a leak or you may pull air into the line. Neither is desirable.
While the gas tank is empty clean out any debris.
Steering
I'm sure when he says "grease fittings" he means "use the grease fittings to fill the steering and tilt mechanism with grease". Pump in grease until you see
clean grease coming out of the part that is being lubricated.
If the steering or shifting is stiff consider replacing the steering and/or shift cables.
Battery
There should be a date code or sticker on your battery. A well-maintained starter or hybrid battery should last 3-5 years minimum. Carrying some type of jump starting battery pack is recommended if the battery is in any way suspect. It's actually not a bad idea in any case.
Standing Rigging
Check all of the standing rigging (wire rope). Wrap your hand (protected by a cloth) around the wire rope and slide it down the entire length. The cloth will catch on any broken strands while protecting your hand from punctures. If there is even one broken strand it needs to be replaced. If there is any rust it needs to be replaced. All of the standing rigging is usually replaced at the same time. If one piece is bad then the rest is
usually not far behind.
Check all of the fittings. Anything that is bent, cracked, or corroded should be replaced. Light corrosion can be cleaned up but if you can't adjust a turnbuckle or move a nut it needs to be replaced.
Check both ends of all of the standing rigging connections. Look at the swages and the nuts and bolts. Check the condition of the spreader tips.
Running Rigging
While the mast is down inspect the running rigging (the ropes). Replace any that are frayed or damaged. Make sure that all of the sheaves (pulleys) turn freely and that they are not chipped. Make sure that the rope diameter is appropriate for the sheave.
Mast
Inspect the mast and boom track. Small deformities can usually be bent back into place. Post any that you are not sure of.
On a 20 year-old boat it is likely that there will be fittings and such on the mast and boom that are no longer in use. If you can't tell what something is meant to do just ask. Someone here has likely seen or used it.
Check the mast step and mast base for damage. Pictures on BWY are a good reference for an undamaged part.
Look for damage to the gooseneck. Ditto on BWY.
Anchor
I know you've already anchored out so the anchor worked at least once.
Check the condition and length of the anchor rode (rope and or chain). A good rule of thumb is a minimum of 3x the depth you expect to anchor in and a maximum 7-10x the depth.
Verify that any rope rode is not frayed or damaged and that it has sufficient chain (if any) for the bottom conditions you expect to see. Check the shackle (and/or splice) where the anchor connects to the rode. That is a common failure point. The mix of rope and/or chain is dictated by local bottom conditions.
Compare the anchor style to others you see in your local marina. That is a clue as to the type of anchor that has been found to work locally. There is no perfect anchor for all conditions. Whatever the locals are
actually using is a good starting point.
Consider one or more additional anchors.
Safety
Check your local regulations but these are required in all 50 states AFAIK. Fines for missing equipment can be high. When checking local regulations be aware that you are
under 26'. A 26X is 25' 10".
You should have (in good condition):
Appropriately sized life jackets for all passengers. Some styles
must be worn to be "legal". All must be worn to be effective.
A throw-able flotation device (usually a boat cushion with straps).
A fire extinguisher (in-date and proper type). New regulations require replacing at a certain age.
A signalling device (day and night). This is often flares. Flares have expiration dates. Make sure yours are in-date if that is what you are using.
A sound making device (usually a horn).
Optionally (but highly recommended) at least one marine band radio.
Also optional (but highly recommended) one or more boater education courses from your local coast guard auxiliary chapter.