so i pull my carb out today due to being fed up with it stalling

heres what i found when unscrewing the choke the plastic screw broke.
looking inside the choke it was all nasty/rusty. o ya prior to this the choke was not working.

heres the problem which pull choke do i order the one with the pin or without. now the stock one has the pin does that mean i have to get the one with pin.

im new to this atv stuff i have no prob wrenching on cars

so does the pin do anything (advantage?) or will the one with out the pin work

thanks guys

o ya one more thing the tiny little o ring under diaphram cap it wasnt there do i need this little guy. where can i get hardware store? napa?