Recharging A/C

I have a 97 Grand AM Se and want to recharge the A/C system. I am a cheapass that isn't willing to pay some garage $150 to recharge it for me. I do understand a bit about A/C, but could someone give me complete instructions on this topic, or point me to where I can read up on it.
I know you have to connect the hose to the LOW side and have the engine running and A/C turned up full. I mainly need to know how much R-134a to add, and how much oil. Is there anything important that I should do?
Any input is appreciated.

Go to Walmart and pick up a re-charge kit.
The kit will have a charge indicator and tells you how much charge level is left in the AC system.

The low side cap is usually has a color blue. Located on top side of the AC compressor or a tube before the compressor. Anything that comes out of the AC compressor is the high side.

I am in Canada. Do the sell that stuff at Walmart in Canada? I don't think I've ever seen it there. Then again I wasn't looking for it either. I see lots on EBAY though. Same stuff right?
This is a simple process am I right? I just find it hard to believe that it costs $150can to recharge an A/C. I wouldn't mind the $35 diagnostic if that included the recharge. LIke I said before....I'm cheap.
So....I'll do it myself. Seems simple enough.
Thanks