If you are loosing coolant even though you have low miles on your car it could be the water pump going out already. I feel your pain about not being stock and not having the parts to make it stock again. I think you should be able to do a pressure test on your cooling system and if it is loosing pressure you have a leak. You should be able to do it with a kit from your local auto parts store. It would be a lot easier then getting back to stock and taking it to the dealer.
If you find a problem then you will have to figure out a way to get it to the dealer. The last thing you want is your car go into limp mode and have to have it towed.