I just did this last week for my 94 d90.
The wiring was simple, but it took me 3 tries to get the correct sender....even now some threads are showing on the sender when I installed it.
I went with the M16 x 1.5 sender. It was the only one I could get to thread in. I called VDO tech support and they said not to worry as long as it doesn't leak....
It seems to register correctly at this point
Email me if you have any questions, as it is still fresh in my mind.