First off, you may not even have to remove the stock gear guides. As long as you get the same sized (diameter) nosegear, then it will slip right back into the same guides. i would suggest a fults dual strut as a more reliable gear. You can get them on towerhobbies, or your LHS for around twenty bucks.
You will have to get a new control horn, which should come with a new collar and set screw (the part you stripped).
You can also just replace the collar. It should be a standard sized wheel collar (but I can't remember the exact size right off). I had to do this a couple of times on my alpha 40. This will cost you the least amount of money.
If the gear you get fits into the mounting block, but is too long, cut it off with your dremel.
Hope this helps.
Nosegear can be the most frustrating part of a trainer while you are learning....

Oh, as a side note, lots of times you can use heat to break locktite loose. Get a good soldering iron (I use a 100 W gun) and put it right on the head of the bolt. Let it get good and hot, and then it should back right out.
This also works if you have epoxy on the threads....