GAz gauge sending unit

My gaz gauge is stuck on 1/8 of the tank and weneever i full her up it goes below empty .

i want to have a look at the sending unit "floter" and see if it's not stuck and i wanted to know if theirs any precaution i should take ?

Can i turn the key to the on position while the pump and the sending unit are out of the tank ?

going to try it tonight so please reply quick