I have made an offer on above machine required by a friend.

The owner claims the date and time display in menu bar is unpredictable,
being due to the need for a replacement battery

Owner claims this to be a $10 part and is easy to instal

I have used Macs since the original LISA and am unfamiliar with this battery
issue
Are the above claims correct and is the issue a minor one?

TIA

Tony Wilson