I've danced around this subject for a while now.  I see STG58 kits in excellent condition for about $350, compliance kits around $100, and receivers between $100-$200.

The fine print with the STG58 kits says that only a Class II manufacturer can use them to build a finished rifle, or something along those lines (I don't have the catalog with me right now).

If I get the parts and order a receiver through an FFL am I going to get a visit from the .gov asking what I'm doing with this stuff?  I just want to make sure I'm staying legal.

While there's no absolute guarantee the ATF won't redefine what the laws mean and visit us all someday for now its completely legal to build the rifle you want as long as there aren't any local laws that prohibit owning an FAL.
As long as you use the correct number of compliance parts you are completely legal.
The manufacturing clause is for those wanting to build rifles solely for the purpose of reselling rifles.
You cannot build rifles from parts & sell them for profit.

Yes, You can someday sell your rifle if you decide.