A friend has made a really attractive offer on a Specialized Tricross Singlecross frame.

I was thinking of stripping my Jamis Aurora touring bike of its components and build up the Singlecross frame. Do I need to just get a rear derailleur hanger for this so that I can run a 9 speed cassette? Are there any complicated changes needed to be made to go from fixed to gears?

Essentially what I am asking is that it is a pain in the ass the buildup a singlecross frame to handle a triple chainring and 9-10 speed cassette?