I've had problems transferring power quite recently but thought this was a gearing problem; the bike is due for a service and adjustment this week. I went to take over a car this morning and I ended up pedaling but going nowhere. The Right Hand Crank has sheared of from the chainwheel (or is now separate from it). I have a number of questions:- 1) Am I right in presuming the chainwheel and crank are one piece? 2. How easy is it to replace, or is this a bike shop repair? Cheers.