I did it not so long ago, wasn't fun! I had a 13mm ratchet spanner and managed to turn it one click at a time. Lifesaver that spanner!
I had loosened but not removed the exhaust header (Cylinders 2 and 4 I believe) to give a little more access, and dropped the front suspension brace so that as the bolt loosened I could pull the mount away from the engine, rather than the bolt rising into the manifold. To get spanner space I also had to remove the intermediate shaft of the steering column.
The bolt hole on the engine support is slotted, so that once the mount is off you can slide the bolt out sideways to replace it with a shiny new one. You're probably aware but if you're replacing the old style mounts with new style you will need shorter bolts than the originals - I can't remember lengths though unfortunately.
Once the bolt was out, the engine mount came out forward into the engine bay and was surprisingly well trapped! I had to release the tensioner to the power steering pump and fold it out of the way, and remove the inner mount for the ARB in order to clear a path to get the mount out, and the new mount in.
Pain of a job, but well worth doing. Good luck!
