Mel, if there are areas of unsealed wood, etc. it may take great effort to get the stench out.
Start by removing everything in the cabin. Any upholstery gets laundered, and cushions go out for steam cleaning--the stink will be IN the foam. Any electronics? There's a film of tar and nicotine inside them all, you can wait a long time for it to cook off, or use solder flux remover or circuit board cleaner to hose them down. This is not for the faint of heart.
Check on the web--any home can be de-stenched from ciggies but it takes some effort. The other "Hail Mary" pass is to rent an ozone generator and oxidize the hell out of the cabin, turn it on, seal it up, air out and repeat a few times.
Oh, and every non-porous surface like the countertops, sealed wood, bilge, hull sides, needs to be cleaned just like you were trying to clean up after hosting plague victims.
The good news is that you'll have a real clean boat when you're done.
A couple of solar vents will help keep the fresh air coming and the residual stink from building back up again.