CLR for the shower doors.
For the smoke, that's a really hard one. Cigarette smoke is very difficult to eradicate - and there are people who are so sensitive that even the slightest remnant can trigger breathing issues.
I would use a good solid cleaner - chlorox, pine sol, etc. for all hard surfaces. I would rent a rug doctor for the carpet (the household carpet cleaners and/or home use machines are not as powerful as the rug doctor). I would wash any cushion covers (or use the rug doctor on them if they can't be removed) - same with the blinds. I would remove all cushions, mattresses and blinds and let dry out in the fresh air.
Then I would use something like Natural Remedy to spray throughout the RV and then open all windows and let air out for several days (the longer the better).
In the end, I would not advertise as "smoke-free" no matter how good it appears, and if someone asks, be honest and say "Yes, we did smoke in it. This is how we've cleaned it up for sale..."