Transmission Slipping Please help

[gee55987]

I own a 1996 with about 200,000 miles. I noticed it would like to drag the shifts from 2nd to 3rd and 3rd to fourth but never really saw it as a problem. As of now the car barley will shift into fourth and 3rd is not all there. It tends to drag under heavy loads. First and second are just fine. Im thinking it has something to do with the Line pressure. I have been doing some research on it and found that Solenoid A valve goes bad. Now if that is the problem I have no idea where to find this or how to replace it. I thought I once read something about resisting the pressure but I'm totally lost with that. Also I thought I read something about cutting a line which would give me hard shifts. Thats fine I just want to get a little more life out of her. I'm totally lost as to what to do and any info would help!
Thanks