Hi Mike;
The nice thing about something like the dxcc is that it won't require 
much of a tuner.  An internal tuner will be more than adequate.  Not 
sure how well the internal tuner will work with the g5rv.
As for that poor neglected tower, is it in a position that you can hang 
the center of a wire antenna from it?  You should be able to manage some 
type of pulley arrangement so you don't have to climb the thing every 
time you put up a new wire.

-- 
richard