Now if Neurotex was around still, he'd have some pointers, that guy was a stick and tissue guru! Wonder where he went off to...
Anyway, the Guillows and other model kits like it are ideal for conversions, and they have been converted many many times over so there is a ton of info out there. If you do a search here on RCU, RCGroups, or even on Google, searching something simple like Guillows RC conversion, you'll get a ton of hits. If there's one plane in particular that you're wanting to convert, my bet is its been converted at least once before and its still floating around in the e-world, just waiting to be searched for.
The only draw back to Guillows is their tendency to use overly-heavy balsa. A lot of folks actually replace all the stock balsa with a better, lighter quality balsa, but its not always needed, depending on the RC gear you plan to use and which plane you plan to convert (some planes just have less balsa). All the new ParkZone gear from the Vapor, Cessna, Ember and the like are perfect for these planes, or even AeroAce gear can do the job sometimes. In fact, there's so many possibilities between planes and electronics, that deciding on just one is usually the hardest part
If you build/convert one, please do post it
Nick