Joy and I put one in a 74 Super Beetle somewhere between 15 and 20 years ago. It wasn't too bad and ended up looking pretty good. It did have a couple of small wrinkles in it, but the headliner was a cheap aftermarket one (I think we paid $29 for it) and neither of us had ever done any interior work. Like Travis mentioned, the windows need to be out of it. We had the windows of ours to paint it, so it wasn't an issue. After we finished, we installed the windows with new seals. It's time consuming and isn't "easy-peasy" but it's within the realm of most do-it-yourselfers IF you have some time and lots of patience.
The headliner glues over the lip the window seals go over at the top of the windshield and all around the quarter windows and rear windows. There are a few metal bows that go through pockets on the top side of the headliner to hold it up in the middle, and the edge tucks under a lip over the doors. If you do it yourself, it's best to have help to keep it stretched tight and straight. Glue the front onto the windshield lip and start working towards the back. Use GOOD spray adhesive . . . the cheap stuff won't hold. I used little spring clamps like you use for small stacks of paper to hold it in place while it dried.
I don't know of a shop to recommend, but any good automotive upholstery shop that works on OLD cars should be able to do it. Modern headliners are glued to foam board and held in by plastic trim . . . Just about anyone can do a good job with those. It takes a lot more time and skill to properly install an old-school headliner . . . which probably equals a bigger price tag.
