Anritsu MG3633A Battery

[Dobby]

I have an Anritsu MG3633 Signal Synth I'm breathing new life into.  I see it has a battery soldered on the control board and the user manual says 'Send it back to Anritsu for replacement at 7 years'.   Does this battery power memory to save only user config settings or does it also save cal data ?  Should I replace it ? It currently reads 3.0V. If so, what precautions does one take  - eg supplying external power to those terminals (via 1k) whilst replacing it ? Many Thanks.