How long would it generally take you to set up an IMac and transfer files from my old PC.

No problem.  Setting up AppleTV and Time Capsule should only take a few minutes however the more time consuming task comes when windows gets involved.  Since there is no reliable way to know how Windows will act at any given moment, the best case scenario for data transfer is usually one hour.  Moving files then importing them into the proper place can sometimes take around 2 hours.  

I always work as rapidly as I can but with Windows I've come to expect anything.  If the computer is in good health then we shouldn't have problems.  Most of the time, I usually pull the drive out of the windows machine then transfer the data directly therefore avoiding the hassle of networking the two machines.  It's the fastest way.