Well I have more experience with Mk1's and Mk3's but I am sure it's safe to say a Mk2 is right there in-between in terms of design and easy to work on etc.
The mk1 to mk3 are all rather simple to understand if you've got some experience with working on cars, rather self-explanitory too.
I myself started working on cars by working on a Mk1, then a Mk3 and so on..
One handy thing to have is a Haynes manual, I am pretty sure those are easy to come by especially for golfs.
Those manuals have all the little tips and info you should need.

One thing to look for when buying one is checking for rust, especially in the fenders and sills under the doors.
I am rather sure others have plenty experience and knowledge about the bad rust areas to look out for.