I assume you're asking about replacing the engine mounts with the same, new ones? And not totally different ones or relocating them.
No different than all other engines. Need something to lift the engine about 2 inches up. So a little more complicated if you just have a socket set.
Just make sure your fan, and wires and hoses or other brackets aren't going to interfere, undo the nuts that hold the engine down, lift up the engine enough to clear the bolts. Might need to loose the transmission mount so you don't tear it (not the cross member, just the mount to the transmission). Unbolt the engine mounts and replace.
Yes, the 2H and the 12HT are the same mounts.
There is not much room between the head/valve cover and the fire wall when you start to tilt/lift the engine. You will need to loosen the 4 transmission bolts. The fan will hit the fan shroud... you will need to watch that.
I don't think using a jack to lift the engine is a good idea. There is no real good place to lift from underneath. An engine hoist would be best and there is enough room in there so you won't have to remove the hood.
Good luck. I just put a 12HT into my HJ60 and manoeuvring the engine into the mounts was a P.I.T.A.