I can also recommend the fiberglass masts. These are support poles for military camouflage netting, and are very strong. You can load quite a lot of pressure onto these before they'll fail.
That said, they're not designed for antenna support, so YMMV. You'll also need to guy the mast, so you'll need ropes and guy rings.
Fair Radio Sales (visit: http://www.fairradio.com/antenn.htm
) has, at the top of the referenced page, a kit for a (basically) 30' mast which contains the fiberglass polesets, stakes, guys rings, and ropes, all in a convenient rubberized carrying bag. A bit more expensive, yes, but I'm thinking that by the time you add in all the other stuff you'll need to set up the eBay mast, you'll be close to the Fair Radio price anyway.
Also, you'll need some sort of base upon which to place the mast. Look at AB-154/RC-292 Swivel Base with Base Plate on the web page I referenced above. You'll need to adapt this to the fiberglass mast, but that's something you can do with PVC.
Have fun, and let us know how it turns out!