Greetings fellas (all of you) and welcome to the Forum.
SantaHoyt,
As far as I know, any of the mechanical hookup can be done by the homeowner.
True, when it comes to the Closed System (Freon) you need to let a Licensed Tech do that.
As far as a recommendation about "ease", we need to know a little more about what exactly you're working with, is it...
That you're going to separate the Blower from the Furnace, and drop an Evaporator in-line, is that it?
If that's the case, having them approximately the same size square, would really help !
Have a good Day !
S.W.