Hey Everyone, I need some help

I have an 89 300E and the A/C blows nothing but warm air. I honestly had to pull over half way through my commute (3.5 hours) because I thought I was going to pass out at the wheel. The only problem I have, is that the car has 207k on it, and im not planning on keeping it longer than next spring. Im not about to drop 700 to take it to the dealer and get it fixed. It still has the original AC in it (R12 I believe it is) and I just want to give it a shot of R12. Which brings me to my next problem, where do I get R12 (if your even allowed to buy it) and then how do I put it in. On ebay I see you can buy the little hoses to Recharge the stuff but I wouldnt know where the Freon goes. Can somebody please help me out. I kinda need to get it done by this weekend (I have my mom's car while she is out of town), and Im not looking to pass out at the wheel anytime soon. Thanks in Advance.

Drew