Stuck float type fuel sender

I have what appears to be a stuck float type fuel sender in my newly acquired RV-4. The wiring and the gauge is fine. It is indicating 3/4 tank regardless of fuel level. If I rock the a/c it does not move. The open circuit resistance is 66 ohms which seems to be consistant with 3/4 tank. I suspect the float has either stuck in position or has failed in some other way. I have tried gently tapping on the inboard portion of the tank where the sender is located hoping to dislodge it but no luck. Any ideas? I have heard of others with stuck floats that freed them somehow. As a last resort, what is involved in removing the sending unit to inspect/repair/replace? Can this be done with the tank installed through the wing root once the fairing strip is removed or do I need to pull the tank from the wing?

Thanks!