Tag Heuer F1 Chrono (CA1211-RO) battery and screw

Hi guys,
I opened my Tag Heuer F1 Chrono (CA1211-RO) to change the battery and I saw a loose screw (or broken screw).
Two questions:
1- The battery type inside is a Varta 394. In my web search, I think the right battery is a 395. Anybody knows who's the right battery type for this watch?

2- In my image, you knows if the hole to the loose/broken screw are well sign? If are broken, are any problem to leave the broken screw in place (I think it's a hard work to change it).

If it's working and nothing is rattling around, I'd just leave it and replace the battery.

Thanks. Only when I put the battery a can will see if all it's OK.

If it's work bad....it's easy remove the screw and put another good screw?

Anybody can sell a screw (product nº 58500) for ETA 251.262? I'm in Portugal.