I have a TAG Heuer 980.031L, which I purchased new in the 80's. Other than a couple battery changes, it has never been refurbished. The crystal is badly scratched and I assume all the gaskets need replacing. Am I correct that this takes a 27.5 x 2.5mm crystal? I will get a generic sapphire off eBay but want to order the right one. Do I need to track down an L-form gasket for the crystal? What o-rings do I need? Assuming I get all the parts, is this something a local watch shop can handle? The black on the steel band clasp has worn away to raw steel. Leave it as is or is there something to re-black it that will look nice? Thanks!