Yes, you should replace the mounts in pairs.

I did the mounts on my '86 Turbo last summer. I thought it was a pain in the a**. It's not that the job was difficult, just time consuming and it seemed that more time was spent just removing items to gain access to the mounts.

Getting the car in the air and removing the belly pan was helpful.

Clean the engine before you start, that makes things easier.

Don't know if there are instructions on-line or not. It's actually a straightforward repair. Deep sockets are a must.