if your mechanic "changed" the oil after it dumped fuel into the block it should not be a problem. if it were me i would change the oil again and check it for gas. also i recommend that you do what Matt1981CJ7 described and work from there.
Only in America do you have the God given right to be loudly opinionated about something that you are completly ignorant of.
The drip is coming from the header/head pipe coupling and it is black... Which I guess means fuel
It's quite normal for the exhaust to drip, or spray, a little liquid when warming up. That is just condensation that develops as the system cools down being forced out. Often times it will have black sooty deposits in it, if your exhaust system is old. The drip/spray should go away in just a few seconds as the pipes heat up.
As for over-heating, I think it depends on the size of the leak. Yes, a major head gasket failure will cause over-heating, a small leak may not.
Have you even pulled the plugs to see what they look like?
I'll almost garuntee it's the gasket. Like I said my brothers head gasket went south because when he bolted it down he forgot to tourqe it and it was fresh rebuild also. I would be making the rebuilder repair it and dont't take it back until it's repaird properly. If the water gets in the oil it will wash the bearings and then it will need another rebuild.
1985 cj with 1992 wrangler body.
Its's a project for now needs more parts and money.
258 in-line 64 speed 4' lift
THAT, is a question for the "mechanic" that did the work for you. As said, don't touch a thing and take it straight back to them.
'84 CJ-7: Yota axles (spartan locked front, e-locked rear) 4" BDS, 1" Daystar & 3/8" shackle lifts, 35" X-Terrains on steelies, YJ Tub & family roll bar, heater blower upgrade, 4.2L w/MC2100 & Team Rush, Warn 8274. Rebuilt 4.2/4.0 hybrid, AX15 and twin sticks/clocking ring waiting to go in.
The advertised position for a topless, dirty jeep girl has been filled......by my wife. Thanks to all that applied.
<------------and yes, that is her. :-D