I can't imagine it would be too easy to do it directly. Having said that, there is a lot you can do by copying and pasting the information into MS Word, and hitting the <cntrl> F button and using the replace feature. That way you could preserve all the node and member info, and replace commas with semicolons or vice versa, whatever proves to be needed. That way, with a bit of hand editing you could probably convert the file much quicker than by having to regenerate it by hand. It's been years since I've used GTStrudl so I can't remember it's specific format, but, in general, that approach would likely work.