One thought - have you tried playing around with any of the guitar software like Guitar Pro?

The reason I suggest that one is that it is easy to enter a tune via the virtual piano keyboard it has there and then to see it played back on a guitar neck. From that you can sort of plan where the melody would fall across the strings (if that makes sense).

It has a free 30 day period (which in fact works for a good deal longer than that) and it's main limitation is that you can't print out long pieces (plenty for a verse of a tune though).

It will also import from ascii and midi I believe but that is probably in a bought version.

Might be useful