in tank filter replacemen with insert / carb float

the carb had a drip from the bottom vent tube. since i ‘ve had 2 different rebuild kits, one from the shop that duzzzz partial work, one i got when i redid their work,.. can a float that does not leak air, from an under water test, still need replacement?{on my 2000}. also, there might have been a speck of dirt where the seat is, whitish, causing the problem.
the shut off on gas tank is also not shutting off. it’s old also. it was working. i might have put a chemical through it, and made it’s demise. {if it works leave it alone} there could have been dirt in there. flow still works. the screen was also flaking this time, i took off the petcock. i got a new screen, before i realized it will be with the new petcock i get, when i finally some extra money. i have to get a temporary shut off for a while.
new filter has a rubber insert, i believe it goes at the segment in the filter that is the in between of, on and reserve. the old filter was hard to get out. pressed maybe. the new one is hard to get in. i cant use my fingers anyway. is there a trick to getting the filter to seat? //ED