Help to get grandfathers watch fixed

hello I’m hoping you can help. This is my father in laws Omega. It recently stopped working and we would like to get it fixed for his 90th birthday. As far as we know it was bought in the US in the late 70s or early 80s. The watch still has the original band 558 and is an automatic Seamaster and looks to be gold plated.

My FIL can’t recall servicing the watch in all the time he’s had it! Overall considering it was worn everyday for over 50 years it’s in reasonable condition although the glass is pretty banged up around the sides and will probably need replacing.

My question is where should I go to get it fixed. We live in Melbourne, Australia. Any other information you can provide about the watch would be appreciated.