My friend is scheduled to have prostate cancer surgery in a few days. What should he expect as far as post surgery complications are concerned?

Hopefully few. The most common surgical risks are bleeding, damage to structures/organs surrounding the prostate and post-surgical infection. With the advancement of minimally invasive surgery/robotics, many of these risks have decreased. However, also depends on surgeon experience and patient factors as well. There is also risks of incontinence and erectile dysfunction following any prostate procedure.
Know possibilities. You should never have surgery without discussing the risks and complications as well as expected side effects directly from the surgeon. A consent is mandatory and when it's signed it means all of this is understood. An incision and catheter is expected. There can be bleeding, infection and pain as possibilities. Though less common he may come out of it incontinent and impotent.
Depends. Outcomes vary based on technique and type of procedure.