base gasket
I just removed both heads on my 748 to replace all rockers. In doing so, it was unavoidable to disturb both base gasket seals. This meant I had to pull jugs.
To make a very long story short, it is a royal pain with the motor in the frame to replace wrist pin clips while balancing the cyclinders on pistons up to the rings. I saw NO way to slide the jugs on after doing the clips. You need a ring compressor because the chamfers on the bottoms of the jugs do not work at compressing the rings as you slide the jugs down.
I think if I was to do it again, I'd consider shooting myself first. Then I'd look for a used 996 motor to drop inplace of the 748, if I was going to go to all the trouble of removing the engine from the frame. My bike only had 7000 miles on it so I reused the rings. Hold on to your hat when you get the price of the head gasket.
The only special tool you need is the head nut wrench. I made mine for the price of a couple of cheap wrenches and a 1/2" drive socket. Search here on the site. Someone posted a pic not too long ago.
Good Luck, I hope I didn't paint too ugly a picture for you. It certainly is doable, but you will most likely expand your vocabulary some.
Good Luck