You've left it a bit late if you're going tomorrow! First off, what are you expecting performance wise? The G is a nice gentle plodder, reasonable performance for a 350, cruise at 50 with about 65 available. Ride is solid, rigid rear might cause jars if you have a bad back. Fuel economy will be good! No real problems with the machine itself, remember this bike was the pre-War 350 Bullet and went on to be one of the better Military machines of WW2 before becoming Enfield's post War second string 350, the ohv Bullet taking top spot. Spares situation is very good at the moment from our Hosts. Original tinware might be difficult though. Areas to look for are same as any old bike, does it start (carb, magneto ok?) and do the lights work (dynamo, regulator)? Does it smoke when running? Do the gears shift ok? Are the wheel bearings/steering head bearings ok? Chain and sprockets ok? Tyres ok? You don't say what price might be, take some pics and show us for further suggestions. Good luck,
REgards, Mark