Good luck! I had a Century III (I think - it was a while ago). I spent a lot of money getting it to work when I bought the plane - it had clearly never been used for years. During its occasional working moments it did a very nice job - full three-axis, coupled approaches, etc, and pretty stable in mod turbulence. But then it started to fail again in various ways, and each time my local avionics shop would find corroded connectors etc and replace/repair them. Finally though it became unrepairable - or at least they said they'd repaired it, but when it wqent into a 1000 fpm dive at 400' on a coupled approach I decided it was time for a new one. The installed cost of the replacement STEC-30 was less than I'd spent on repairs :-(.
Honestly I would just forget it and buy a new one. It'll cost you less in the long run and it might even actually work.