On a scale of 1 to 10, how difficult is it to fit?
You should be able to replace the inner part of the valve, though baring in mind the cost of the specific screw then replacement part, you'd probably be cheaper getting the entire thing replaced?
1) Remove wheel
2) Remove tyre
3) Change valve
4) Replace tyre
5) Balance wheel
6) Replace wheel
7) Alls well
You won't DIY this one, it'll cost about £5 to £10.
You dont have to do all that, simply let down the tyre, break the seal on one side, slice old valve out and pull new one in before sticking it back to required air pressure. Job done.
.... break the seal on one side ...