When I ran my coax for the antenna, it really wasn't difficult at all. I took the cap off the top, pulled out a block of foam and pushed the fishtape down the mast next to the foam until it came out the base of the mast. Then I pulled the wire back up from the bottom. If you want, you can tie wire ties every few feet to hold the wires tight against the inside of the mast to prevent clanking. The wire ties will act like springs inside the mast. The Styrofoam at the top of the mast will act as a strain relief for the wires.
The fishtape mentioned above is just a very stiff coiled wire that electricians use to pull wire through walls and such and can be bought inexpensively at hardware stores. It worked like a champ for me.
This thread describes how I did it.
