What is the best way to attach fondant...gum paste...and especially modeling choc. to a sculpted RKT shape???? Please Help?

You could brush it with a little bit of corn syrup or even rub a bit of shortening over the surface of the RKT before attaching the fondant of modeling chocolate. That should help it stick!

Did you cover you rkt figure with something to smooth out any lumps?  Such as white chocolate, bc, ganache? Then just moisten the back side of your fondant or gumpaste and it will stick.  Do not add too much water, just a lite mist.

no i havent...its a giant tree...kinda like a maple..
 

So maybe you want the tree trunk & branches to be on the bumpy side.

everything is turning out wonderfully...thank you all sooo much for all the help!
 

Glad things are turning out well for you. Post a pic when your done.