Mouthpieces really aren't that easy to fix and you'd probably come out ahead just buying a new one and taking care of it. Shanks can be trued, but dings and scratches are difficult and labor intensive to fix, and simply having the mouthpiece replated won't make things any better.
From Lee Stofer:
Restoration of mouthpieces that are currently in production is often not economical, as you can buy a new one for less than what a restoration costs. However, if you have a historical mouthpiece, or one that is just your favorite and you want it restored, I will do that for you. Just please bear in mind that I generally try to do several at one time, as multiple mouthpiece plating orders at the plater's saves on my cost, which saves on your cost. If I were to do one mouthpiece by itself and have it silver- and gold-plated by itself (gold-plating needs a good base of silver plate to adhere well), the cost on a one-only mouthpiece would be $150.00 or more, whereas if I get 4 or more done at one time, I can drop the price by one half. Mouthpiece orders sometimes take a while, so I ask for your patience if you get a mouthpiece restored. I can get it done quickly, but it will be much more costly.
The minimum charge for mouthpiece work involving buffing and re-plating is $50.00 for smaller mouthpieces, and $75.00 for tuba mouthpieces. One mouthpiece is restored with each full instrument restoration, and is included in the full instrument restoration price. Restoring a mouthpiece can be extremely time-consuming. I am willing to restore just about any mouthpiece. Just be aware that if the mouthpiece is in really rough condition, restoration could cost several times that of a new mouthpiece. That is why I suggest limiting mouthpiece restoration to those of historical significance, great rarity, or mouthpieces that just play great and should be preserved. Mouthpiece shank trueing is a minor operation, and done for $5.00 or less.
