I'm still new, so take what I have to say with a grain of salt, okay?
Definitely cut/file his nails down as short as possible without causing him any discomfort- don't wait until just before the show in case you accidently cut too short and cause any pain (not a good thing to go into a show with a lame dog because of cutting a nail too short, etc.). I tend to Dremel both of my dogs approx. every 10-14 days to try to *keep* them short.
As far as trimming, don't trim whiskers and try to avoid trimming the twizzle (end of the tail) for a specialty show. You can "neaten" the feet a bit by getting some of the excessive hair off that may be sticking out between toes and whatnot, but don't get too "scissor happy" because you want your lab to have hair!

LOL Most likely, you'll be showing outdoors anyhow, on the grass? The feet will likely be covered up by grass when free-stacked in the ring.
Specialty shows typically have breeder-judges, so they tend to like labs more au-naturale (is that how you spell that?) than an all-breed judge who is used to dogs with a lot of grooming. I have gotten to the point where although I was once taught to bathe my dogs before shows, I simply don't do it anymore- I can't remember the last time I gave mine a bath. At most, I'll spritz them down with diluted Listerine-water to tone down any muddy-wet-dog smell they may be trying to carry in with them (especially since they're house-dogs), but usually I don't have to (because they're house-dogs). I also tend to rinse them with fresh hose water after they've been playing in our chlorinated pool. They are supposed to feel a bit oily- that oil on their coat that helps with the water-repellent nature of it. Two different judges at a specialty show I was at this fall really lectured people for bathing their dogs. LOL
Does that help at all? Are there any "special needs" areas that you need to work on such as a cowlick causing a topline problem, etc.?