AC question

[phlegm]

The post on R-12 replacements got me thinking. Is it worth it for me to purchase the Frezee 12 kit, 80 bucks on Ebay, with the check valve so i can check and fill myself? How hard is it to do, I hear it can be dangerous if you are not sure what you are doing. My AC works well once on the highway, but arround town it is luke cool at best. My father in law says it needs a shot, but I am not sure. I think it its low when I test it the way my haynes manual says(grabbing the 2 pipes to see if air temp is different).

There is a place in town that can do the R-12 check and replacement with approved coolant, but if in the long run its cheaper I would rather do it myself.