Other than the under torqued factory head, the only other real issues will vary depending on how well a 25yr old turbo car was taken care of. Of course, if it has suffered overheating in the past, whether due to bhg issues or otherwise, then it may suffer a few more related issues.
I imagine you'll do all the normal craps, ie; hg and retorque & all things cooling related (hoses, water pump, oil passages cleared, cap, etc.). Other than that, as Geeesammy mentioned, they do have their own little quirks and tricks to be learned to fine tune the vehicle. Until you're more experienced, knowing someone who's super familiar with the 7M will go a long way.
I've been considering selling mine and I've found that parts are hard to find, now. 5-10yrs ago these things were everywhere you looked. Now, buying a complete car can range greatly in pricing depending on condition.
Wonderful GT car. Handles great for its weight, eats miles up and is always comfortable and relatively quiet. And for those MKIII haters, I've had MKIV owners in my car who liked it more. Not many, lol, but whatever!
If Geeesammy can't help you, pm me and I'll do what I can, as well.