2000 Escalade Fuel Guage Problem

My truck has a problem with the fuel guage. When I turn the key to the run position, before I start the engine, the fuel gauge goes all the way past full and pegs out for about a half a second and then it comes down to being close to the appropriate volume. It then shakes at that volume around a quarter tank or so which is close to the actual volume. I had a new fuel pump and sending unit installed in March of 2006 and in May of 2007 they replaced the 4 pin connector. I have only put about 25,000 miles on it since the new connector was installed. It is the older style 4 pin square connector. Should I replace the fuel pump and sending unit with a newer 4 pin flat connector, or do you think the problem is somewhere else? I heard it's possible it is in the instrument cluster. The truck has a total of 120,000 miles on it.

Thanks,
Jim