Purge for oil temp probe replacement?

I’d say no as long as you don’t loose too much oil.

These senders rarely ever go bad. Did this just all of a sudden start? If this is a new setup and you have a digital instrument you may just need to change a setting in the instrument. 

First you can try something else. The VDO oil temp sensor is the same one as the #2 CHT sensor. Just swap the wires and go fly and see if anything changes or if it's the same. Quick, easy and less expensive.

If you do want to replace the sender then it's quick and easy. When you are ready to swap them unscrew the first sender most of the way out. have the new sender ready to go in the other hand. If you have something like an radiator under this area place a paper towel or rag over it for the few drops that may come out. When the first sender comes out immediately put the new sender in. Very little oil loss and you do not need to do a purge. The amount of oil loss will be negligible. 

Sounds like solid recommendations. When the rain goes away, in a couple of days, I’ll follow your advice. Thanks guys!