you're having an IM rod / nail inserted. They are often used in acute fracturs of the tibia and femur, but as I recall your injury was some time ago. Is there a malunion or something?
Complications are likely to be the same for all bits of metal inserted into bones. Essentially, infection and blood loss during and after surgery. They are also quite sore, but I'm sure your anaesthetist will sort you out for some good post operative pain relief.
Lots and lots of things can go wrong, but they rarely do. Your surgeon will discuss all these things with you when you sign a consent form.
wolfie, if you want my (anaesthetic) view, then feel free to message me. I'd be happy to help as best I can :o) (My dad and my father in law are also orthopaedic surgeons :o)!)
Totally depends wolife3000 on why exactly you're having the surgery, but generally orthopods try and get their patients up and about pretty quickly. As a rule of thumb it takes 6 weeks for a simple fracture to heal, and you'd expect to be more mobile after a week or two, but without details I'm really just speculating. Hip replacements are up and walking the very next day!
I'm sure your GP would not mind at all 'being bothered' :)