Gary,

1. working lcd/lcd models are VERY scarce: since I collect I saw only 2-3 working: all others defect ( and I saw many defects: about 90 offered on ebay in the last 10 years)
2. the back can be opened with a sharp knife or screw driver: just lift the back where the numbers have been engraved from the main case.
3. battery exchange is easy: but get to a watch maker if you are not used to it. the module is Very sensitive.
4. if the LCD moduls are already darkened: forget about exchanging batteries
5. there a NO whatsoever spare lcd parts available: not at Heuer and not at collectors
6. if not working sell ASAP as its a waste of time and money.
7. you than only get some money if the case and bracelet is NEW Old Stock.

rgds
Alex