The black eagle was done in memorial to Mr Sturm, the earlies models had a red one.
Ok, changing the barrel on a Mk I or standard model is not a trivial task, Changing the entire "upper" on the frame is simple. However, unlike most pistols where the frame is the serial # part (and legally the firearm) the Ruger has the serial # on the receiver tube (the action).
I'm not certain, but I think the barrel is press fitted into the receiver. If so, its not a job for the average small shop gunsmiith.
I'd call Ruger, first, and see if they are willing/able to do the work. If not, then I'd call one of the major shops specializing in Ruger custom work.