the reverse light switch is two wires...yellow and blue i believe. you could allways take the switch out of the tranny and hit it manually to test it.

check your tach wire from the dizzy with an meter or test light see if it works there if it does continue to check then the harness plug then behind the cluster.

and yes there is a fuel sending unit in the tank...you access it from under the rear storage compartment..

by chance do you think you cluster might be bad?

also check your fuse box...the whole thing could be bad....

it happened to a customers car of mine once.