replacement. Have code p520. Can any body point me to a good how-to source to do this? Thanks

I just replaced one in my 2007 Ram last week. The guy at a NAPA store suggested buying a factory part instead of aftermarket due to reliability issues. $38 at the dealer.
There are TWO senders near the oil filter. The upper one is the oil pressure sender. It is mounted horizontally and points toward the radiator. A 1 1/16" deep socket fits the hex on it. A 6 inch extension and a 1/2" drive ratchet cleared the lower radiator hose. It is fine thread so be ready for that.
The hardest part was removing the retainer to get the wire plug off. There is a sliding red plastic tab that pushes up from the bottom to release the wire plug. I used a long standard flat screwdriver.
Good luck.

You can buy them cheaper on ebay than the dealer, but be careful who you buy from as there are exact copies with part #s and all. Don't waste your time on the cheap aftermarket ones, unless you want to redo it.

Thanks for the replies. Does anyone know if this can be done from the top?