I have a 1997 jetta and the ac is not blowing out cold air?

I have a 1997 volkswagon jetta 4 cyl. and the air is not blowing out cold. I was going to try adding some freon but first i bought a gauge to see what the psi is on the low side because it is supposed to be between 25-45 psi . and it is showing 65 psi. which is in the warning area. so i dont wont to put more in it and overcharge it and mess up the system. is there any way to drain it out yourself and put new freon in it . maybe that will fix the problem . or is it something else. any help is appreciated. thanks!