#1
are there any companies out there that could press small amounts of 12" LPs? I would like to release my album on vinyl too, but would it be practical? what are the going rates?
#2
I can tell you now, it will not be practical, even without knowing exact prices. By the time it is all said and done, you'd have to sell a relatively large ammount to break even.
#3
It depends. For small amounts, vinyl is far too expensive to press, and you'll probably lose money. It costs a lot more than CD's to manufacture, so I'd recommend only doing so if you expect to move fairly high volumes. (As MrPillow said, basically)
There is poetry in despair.
#4
Also, vinyls have a completely different mastering process, so you need a separate vinyl master.

If it is too loud or the bass is in stereo, then the needle will not stay in the groove. Therefore a modern master with everything squashed to within an inch of its life and pumped to the max will fail. The bass is a relatively easy fix, though. The mastering engineer (or whoever has the tools) will send all frequencies below 150Hz to an MS matrix or some form of stereo image device/plug-in and make sure it is all in the middle of the image.