94 w124 Air Conditioning problem

[skiier3_9]

On my 94 e320 my AC works moderately well if the car has been in the shade or other cool area but doesn't seem to be able to "catch up" with the heat and cool sufficiently if the car has been sitting in the sun. At low fan speed i can feel that the air coming out is cool but when the fan is on high (or auto) the air isn't cool at all. After about 30 or 40 minutes of driving around like the A/C is finally caught up and the car is cool. I would expect that it should only take about 5 or 10 minutes for the AC to feel cool on your face etc so i suspect that something isn't working properly. Where in the engine bay can I check the refrigerant level (where is the compressor?) Or is this likely a different issue.

http://image.inkfrog.com/pix/houstoninc/DSC04589.JPG

BTW: I read in a different post that all 94 cars had R134a - can anyone confirm this? If so, I should be able to recharge the system myself (if it is low that is).