I replaced the original relay a few times. Just un-soldered it from the board. Digital is a nice upgrade though. As stated there are only 4 wires that are needed. There are 6 coming off the relay that are soldered on the board, but 2 dont do anything. They would be used in changing the relay function from NC to NO.

Here is the replacement relay I used.
https://www.mouser.com/ProductDetail/65 ... ET130AC120