The fuel gauge can move freely if the car is in park or neutral.

I flipped a new dorman level sensor into my crapbox this Sat. 15min and $20 later, I'm praying the pump doesn't find out I put new parts on the car. lol In all the cars that I've done senders etc..I rarely use a new gasket. New gasket needs a lot of lube typically to get it to seat and sometimes a bit of beating.