The A/C has a thick seal between the part you see on the roof, and the roof itself. If you take off the inside cover (8 or 9 screws) you'll see four bolts which hold the outside parts to the inside parts. Tightening these 4 bolts may solve your problem if they've worked a little loose. However, keep an eye on that roof seal. It shouldn't be tightend down more than 1/2" thick. If you get to that point and it is still leaking you need a new roof seal.
As for the fan leaking, look at the caulk on the roof around the vent. You probably need to remove the old stuff and recaulk - along with the other caulk on the roof around the antenna, sewer vent, etc.