Basmic, is this going to be done by a dentist that's treated you for some time now, and is therefore familiar with your comfortable anaesthetic/adrenalin dose? If so, it should be nothing like the dread experience that it's made out to be.
If not - just make sure that you work with the dentist at the injection stage, and not accept just the first injection unless you're confident that you have no feeling in the right area. Apparently, the amount of anaesthetic/adrenalin required varies significantly between individuals.
Dental technology has also made amazing progress, too, should your last dentist memories be from childhood. Well, I was amazed, anyway.