Some things that worked for me--
Take the weight off the mount and remove the long bolt/nut through the mount first, and when replacing the mount, reinstall it on the engine before you bolt the mount to the frame. I once learned the hard way that bolting the mount on first and then trying to line up the engine just right was a pain without a helper. The mounting holes to the frame are slotted so you have more leeway.
Unbolting the transmission mount can give you more room to raise the engine, but it's not necessary to do the job. I've always recommended replacing the tranny mount at the same time because they degrade too.