If you are a competent home mechanic you'll enjoy working on the GS, it's very straightforward, and rewarding when running sweetly through your own efforts. Lots of nonsense spouted concerning the CANBUS electrics, don't worry as they pretty much take care of themselves. You will definitely need some form of synchronising tool for the throttle bodies, such as a home-made manometer, carbtune or twinmax. Without it, you'll never get the best from the boxer twin.
When refitting the rocker covers after checking the valves, take care with the seal for the spark plug tube, otherwise you'll get oil all over your boots next time you ride. Reseat it on the rocker cover before fitting.
A wealth of info in the public domain on UKGSer and ADVrider etc, do your homework for the tips and tricks and you'll have no worries.
It's worth subscribing to the forum for a small annual fee to help this service to exist, but that's your choice. And don't be put off by the banter, it sounds hostile to newbies here but it's mostly tongue-in-cheek.