I'll 3rd or 4th the sentiment of keeping a wire wheel away from the gun for any reason. It's worth more as a brown gun than a cleaned up gun, unless done by a professional. If you are "cleaning it up" for him, you shouldnt do much more than regular solvent in the bore and action, and outsides. If it has some minor rust spots, some bronze wool and good oil is all that should be used. 4-0 (0000) steel wool and oil could be used, but the bronze wool is safer. The sticky action may be old dried oil in the action. A few toothbrushing treatments of Hoppes No 9 solvent may loosen up the crud in the rails and smooth it up some. I would strongly reccomend against taking it apart, particulary the cartridge guides. It simply isnt neccesary to take apart a Winchester to clean it, and the chance up buggering up screw heads or losing a small screw isnt worth it for the most part.
Even with the out of focus pictures, it looks like this gun is in decent condition. The wood isnt beat, and it has a fair amount of blue on most metal. Its common, even on rather high percentage condition guns for the receiver to silver out long before the other parts do.
Most of the early type carbines I've seen for sale have been in the $600 to $1200 range, depending on condition. Even a pretty well worn, original condition (no wire wheels ever came near them) gun will bring the lower figure for an early type, commonly called a "Saddle Ring Carbine" or SRC. This gun would probably bring towards the mid to higher end of the price range. Clear pics would help tho.
If the gun is basically sound it should be safe to shoot with factory or equivalent ammo. All the 1894's in 30 WCF (30-30) were made with decent steel and are up to factory level loads. The primers may back out slightly, this isnt uncommon, and doesnt cause any problems if it isnt excessive. They can do it even with headspace in spec, but slightly out of spec isnt going to cause any trauma. The round doesnt consistantly generate enough pressure to push the shell head back against the bolt face to reseat the primer. Read P O Ackleys experiments with Winchester 94's if you get the chance.
If you get a saddle ring for it (Winchester called them "sling rings" back in the day) you need the older type, which is about a 1/4" shank size. The later cosmetic saddle rings used on commemoratives and recent guns are a much smaller shank size. Several Winchester parts guys have the rings and studs available.