Congrats on your purchase. I just grabbed a mildly modded 95 GT off a local car dealer who didnt know what he had. Yea, the clock says 139K, but the car is tight and runs like a banshee with its azz on fire. I paid a bit more than you though .. $4250 was drained from my bank account ... but worth every penny.
Following what has already been posted, just start at the front of the car and work your way back. Check everything and anything that could be worn and need replacing or cleaning.