New Oil Pressure Sender Unit for 94 E420?

[screedchan]

Recently, my oil pressure gauge started behaving erratically, sometimes working, but most of the time dead. While in the shop for something unrelated, the mechanic thought that it needed a new sending unit. I don't know anything about the sending unit, where it is located, etc., but just wonder if it is something I can do myself. Also, is his diagnosis correct? Thanks in advance for any helpful replies.