You'd end up spending at least $100., probably more. Call around and see if there are any vets in your area who offer low-cost services; or if that's not a concern, find one who knows something about small furries. A mobile vet who comes to your home would be best, as these small critters get stressed out easily when they are already not well.
I've nursed sick mousies back to health, I've also had the experience of getting one back to what I thought was good health only to see it expire just as I thought all was well. Another option would be to deal with this your self, research the non-prescription or easily acquired remedies.