On a 172? Well I watched K-Tec do 2 of mine the other week and ...
Easiest one is the bottom Dog Bone. 2 x nuts/bolts. 1 minute job.
One under the battery is complicated by the fact that the battery is so tight and fiddly to get out. Once youve done that then reasonably easy. Biggest problem was that the stud bolt in the gearbox started unscrewing from gearbox end rather than letting the big nut on top of the mount release. Also dont drop the bolts that fix the mount to body down onto the gearbox.
Havent done the expensive looking hydraulic one on the drivers side yet. But looks fairly easy. Only took 30 secs to loosen it from body, and shift for a few mms, trying to stop my exhaust manifold hitting the heat shield when Im giving it some.