sending unit to gas tank

I have my new tank and now a sending unit (thanks JD340)All are new.I need to get out of the house today. My question is.....seal to tank then sendingunit then locking cam in that order,correct and also would you in stall the unit before painting the tank and undercoat it/stone guard for protection. Any thoughts appreciated.BTW im in Ontario so painting it will be in home......to cold.