Airconditioning

I have a 1987 911. The AC temp is 61 degrees.
I checked the freon level. It is hard to see but I do not see any ball behind the glass.
Do I need to add freon. Can I do this myself.
If not how much should it cost.
Thanks

I need to have freon added about every other year. I took my to the dealer and it cost just over $100. The one thing that happened last time.... they added too much and it did not cool as well. They removed some and it worked much better. (this is why I don't do it myself).

Should be about a 20 degree differential in air going into evaporator (interior temp) and air out of vents. Make sure your condensors are clean and if you have fans on them make sure they are running.