Ok, I've not ridden a bike with a front mech for nearly 5 years now, what with riding SS and DH bikes. But now I've buggered my cranks, I plan to get new ones with a 22-32-bashguard setup, and turn into some kind of "freeride" (spit) monster. Thing is, I've not got a clue about the following:

-I have an old STX-RC front mech lying about. Will this fit on a 9spd setup? If not, what mech should I go for? It's one that attaches to the frame.
-I imagine most shifters are made for 3 front chainrings. To run two, is it as simple as winding the high limit screw in or is there more to it?
-Are there special two-speed front shifters available?
-I know there's lots of types like top-pull, bottom-swing and all that; are they frame-specific? In other words, will my frame dictate what type I need?

Thanks for any help, I really do know nothing about front mechs any more!

Yes
Yes
No
Yes

Or more fully...

STX-RC will work fine with a 9 speed setup, even though it is an 8-speed mech. The chain cage will be 9/8ths wider than it needs to be, but should cause no problems.

Although I've not tried it, that really should work.

Lots of road shifters are 2-ring, but they aren't going to fit. There are no 2-ring specific MTB shifters.

Which type you use depends on your frame. If your cable goes under the bottom bracket, you need a bottom pull mech. Otherwise top pull. Top swing mechs have the cage above the clamp thus requiring only a very short 'seat tube' - they were designed for full suss bikes that didn't have a full seat tube but will fit any bike with a seat tube. Conventional swing mechs have the cage below the clamp so require more seat tube. STX-RC is probably conventional swing. Other than that, you obviously need a clamp size that fits your seat tube - there is a choice of 3.

Buy a Deore top-swing and it'll fit pretty much anything - top or bottom pull, shims for seat tubes. There's a front mech article somewhere - search in Know-How/Maintenance for "front mech" or "transmission" and you should find it. You're right about the limit screw.

Is

Wierd, what's going on there? It didn't like those links...

Anyway, try this -

http://www.bikemagic.com/news/article/mps/UAN/2968/v/4/sp/

for front mech stuff.

my stinky came with a standard lx mech with the high screw wound in for the double chainring setup.

and you don't need a 2 speed shifter as you'll only be able to click a 3 one twice before the limit screw prevents you from shifting further... i had a guy come into our shop looking for a double mtb shifter and didn't seem to believe me when i told him a triple is the same. he walked off saying "i'll try somewhere else", bet he's still looking. :P