Dropped the gas tank to install sending unit.
Filled up today (for second time since the work was done). Leaking gas underneath. I am guessing i probably didnt secure fill pipe correctly? Drove it a few miles to work and seems like it has stopped.

 

gas leaks aren't anything to mess with. you should get under there ASAP and figure out where it came from, and tighten or fix whatever failed. could be the fill pipe, the carbon canister vent tubing, or the fuel lines, or the seal around the pump/sender assembly access plate.

 

Most likely the Bung Nut is not seated well. When you replaced the sender you left it loose or more likely it did not tread properly.