A permit is required to purchase a handgun, no exceptions. Takes anywhere from a few minutes if you have connections or up to around 10 days if you have a lazy sheriffs departmant or police department.
Long guns can be purchased without a Firearms Purchase Certificate. The dealer has to call it in. It takes him time away from helping other customers and he could lose a sale due to you being inconsiderate and not planning ahead. Some dealers refuse to call it in, and I don't blame them. I would charge you $25 for my time if I was a dealer.
Without the permit, you may be subject to unnecessary delays from the NICS system, up to three days in some circumstances. Having multiple DUI's can lead to a delay, as well as a refusal from NICS (they claim that it means you are violent because you drink and drive).
Get the permit, don't piss off the dealer, avoid the delays, and support small dealers instead of big corporations.