So im about to start a job that I'm fairly replaceable in but I would be pretty good at so my question is should I tell them now that I have a vacation planned in a few months where I'll need to be gone for 4 days or should I wait until I prove myself to be a good worker and then let them know that I really need the time off, or alternatively make up a reason to be gone during the vacation (ie sick child, etc), keep in mind that I will have vacation time but not until a week or two after my planed vacation (I don't get it until after 90 days)