I did this to mine.. Think for all four pillars it cost me about £70 ish so not too bad. As Bilsten said, the B pillars are literally four torx screws each side and will take you about five minutes.
The C pillars are a pain in the arse however.. Took me about an hour to do one, haven't got around to doing the other one as I haven't had time in work! It involves taking the door card off the inside, taking the window off of the regulator, pulling the seal away, unclipping the handle then doing the reverse to fit the new one. While the door card was off I took the opportunity to fix some dynamat on the inside of the door to sound proof it a bit!