Paul,
Jason made a good point and I wouldn't even consider printing them on an inkjet. You can experiment, but pay a buck or two and have them done on a B/W or Color laser. Staples and other places can print em for you. If you have access to one at work, you could use theirs if they don't mind. Set the printer to "Card Stock" for the paper type, otherwise it will print way too thick and smear heavier colors like red.
As far as coating, I coat all my decal sheets after they are printed with MicroScale Decal Film. It's two bucks a bottle and is enough to put a coat or two on about 6 sheets. Paint it on with a brush; it will want to go on thick, so spread it out because even with laser printing, it will bleed if too heavy a coat is applied. Even with as thick as it is, it dries VERY fast!
I use decal film on mine because it adds some thickness to the decal and helps prevent tearing. I have done one coat and two coats and would recomend either. The pics you may have seen of my HARM AGM-88 and Harpoon AGM-84 are all home made decals...it's the only way to go for scales buffs like myself!
Hope this helps,
Carl
TRA 08664 L3
NAR 79454 L3