Transmission issues....

I have a 95 grand prix se 3100 with 110,000miles on it. My transmission shifts hard from 1st to 2nd gear only. All the other gears shift perfect. It will hesitate to shift then finally shift with a heavy shift under normal driving conditions. I poured a bottle of seafoam tranny treatment in it and the shifting from first to second has gotten quite a bit better. If i let it shift at red line from 1st to 2nd it shifts fine. The tranny doesnt appear to slip either.

I plan on changing the fluid in it this weekend. Hopefully this will end the issue. Does anyone have any suggestions on how to make this job easier? I know it can get quite messy. Also, should I take the fluid out of the cooler also?

Thanks!

Could be a sign that 2nd is going out the drums have been known to crack. I would check the Modulator (this usally cause soft shifts) make sure you have good vacuum and there is no ATF inside, pull it off and tip it up so that the area where the vacuum line hooks up is down and see if any ATF comes out. Aslo check the valve behind the modulator make sure it is free only goes in one way so dont worry.