I've done an aftermarket sunroof before, on an s-10 blazer
Honestly, after 4 or so years of having it- it developed a leak
when I took it out to reseal it, it had caused the roof to rust out around the front edge to the point where It could have fallen out completely had I been unlucky. I believe this was caused by the bodyshop when I had my car painted- they left bare metal where the plastic trim ring went and thats exactly where it rotted.
Other then that I never had a problem (well, it did have to be replaced about 3 months after I bought it, but that was due to a bowling ball)
If it's installed correctly, its very nice
If its not, it's something that will ruin your car.