Don't worry about how long your car is going to be of the road.
That is the least of your worries.
My 1200GX is currently in for a repaint.
At the moment it is a month and a half of the road.
Ok. I must admit the guy is very busy.
If he worked only on my car it would have been finished by now.Get a quote from as many people as possible.Check out how their previous jobs look and if possible speak to these people to find out if they are happy with the job.
Everything that can be stripped on the car must be stripped. This is very important.My car is stripped by the doors,bonnet,boot,windows,front left and right pannels above the wheels and little stuff like the badges and stuff.All must be prepaired 100% before the job.While it is being resprayed, buy new rubbers and replace all rubbers.
Where the rust is,clean it up 100% and use the rubber paintable stuff they use on the back of utilities to prevent from rusting in the future again. As the other datsun fans said: "Preparation is the key to a successful paintjob."
If you do not have the experience to do it, like me, rather let it be done by someone and go and do a frequent inspection.
Don't forget to take photos of the whole process. Hope this helps.