how can i get a longer barrel and/or m16 stlye sights

For the longer barrel, you might want to shave off the front sight assembly, then, using set screws or some other means of securing, attach a barrel extension. This would not be a longer barrel per se, but it would give the illusion of such, as well as giving you more room to mount underbarrel acessories. To get a longer barrel, if you know someone with a machine shop they might do it, but IMO it's WAY too much trouble, and would be a bit of a problem to install. When you say M16 style sights, are you talking about front or rear sights? Carry handle sights or A3 style flip up emergency sights? If you want a carry handle style, you could just use one of the aftermarket carry handles that clamp onto a scope rail (meant for the A3/A4 style flat top M16's), but I wouldn't subject it to too much stress, the scope rail on the crosman is by no means the same as one on a flat top AR. Emergency flip up sights like you see on the current issue A3 rifles to back up the red dot sights can be found from any number of online distributors. Front sight assemblies can be found almost anywhere, but it may end up being easier to mount a Kel-Tec Sub 2000 front sight assembly onto the barrel using loc tite, Kel Tec will send you the part if you ask for it and pay the money. Also, with a little bit of jury rigging, it could be possible to rig up a Kalashnikov style front sight. The AR front sight assembly would be a bit mroe difficult than the others, and since all of these sights are calibrated for a high velocity round that is expected to be used anywhere from 10-200 meters (yes, the sights say otherwise, but the effective range of the .223 generally peters out around that), it would be mostly cosmetic. Might just be easier to work up something out of sheet metal, or draw up something on a CAD program and take it to a local machine shop. Just my .02!