RE: Are Guillow's kits any good for practice?
Big Ed, That sounds like one of the OLD Guillows kits. Good Luck!
They are basically small-scale "Builder's Kits". If you can make that thing look good, you'll have NO problem building the Rapture.
But to tell the truth, that Guillows kit will not give you a whole lot of the type of experience you will need for the Rapture. They are just two different animals.
If you really want something to "practice" on, try building a Sig "Wonder" they are pretty cheap ($30?) and use construction that is similar to most of today's kits.
Otherwise, just go ahead and tackle the Rapture. I haven't built one, but I'm familliar enough with GP kits to believe that the Rapture will not be a difficult build.
Keep us posted, and let us know if you hit any snags.