If you are worried about breaking any of the exhaust studs or nuts you could buy new ones before you start the job. That way you can ensure that they go back together nice and easy. I bought a set from a local fastener for a few bucks. they aren't anything fancy.
M8 Exhaust studs and nuts;
Dorman M8 These are M8x1.25 x 40mm
Or a set of M8x1.25 x 25mm bolts
As far as penetrating oil goes, we use KB-88 at our industrial maintenance shop. It is industrial strength and you do not have to wait 24/48 hours. Maybe 10-20 minutes tops. We used to use Kano Kroil but it is really harsh on the body, inside and out. if you can get your hands on ether they will work, just make sure you use any sort of penetrating spray in a well ventilated area.