Fitting Baxi 80e DHW Diaphragm Repair kit ?

Hi All,
As the title says I have a Baxi 80e with a leaking push rod on the DHW pressure differential valve. I have ordered the DHW Diaphragm Repair kit and have read various posts about it. I’ve also read the service manual available via the Parts Arena web site regarding the fitting procedure.

I feel up to doing this myself (looks fairly straight forwards) but just have a few questions:

1) I the service manual says to shut off the primary water circuit; I assume this means turn off the mains water supply (no need to drain the CH water). Is this correct?

2) I’ve read that you need to apply silicon grease to the push rod assembly when refitting (the service manual does not mention this). If so can you point to a type / brand?

3) You have to disconnect the copper sensing pipes from the assembly. Is there anything special about refitting these i.e. do you need to apply any sealing compound / grease?

4) Any other “gotchas” or procedures I should be aware of.

Any help on this would very much appreciated.

Regards,
Ian