Most of the physical consequences of nicotine go away within a couple of weeks. There's a never ending psychological battle, but that is pretty compatible with holding down a job. Find a way to get two weeks off at once if you have to.

As for alcohol, I'll just say that as incompatible as withdrawal is with holding down a job... being drunk is pretty incompatible too. I think if you can finesse one, you can probable finesse the other.

In general, my observation has been that as horrible as withdrawal is, that's the easiest part of kicking a habit.