Not sure if you already have a sign company making your decals or not, but I have a plotter and do signage on the side (mostly a hobby, but I can do some pretty tricky stuff). You would, however, have to apply the decals yourself. You said you would be nervous doing that, but it really is not hard at all, I could send detailed application instructions making it almost fool proof. Let me know if I could help you get this done when you finalize the design. I would charge for materials and shipping only (probably like $15 for the whole back window, which you could send a check after you receive it). Printing a color logo would be a couple bucks more but not much.
I'm extending the vehicle graphics/storefront vinyl to all Technibblers that are actually running a business and want an inside guy with a plotter. I'm not doing this to make money at all, I'm doing this to give back to the community that has helped me tremendously over the last few months, again, I would only charge mats/shipping.
Brice L
P.M. me if your interested. I'll send you my # and we can talk about what you need.