The fuel and oil pressure gauges have to be replaced at the same time since they are a single assembly, but if the slosh module is bad then replacing the gas gauge isn't going to fix the problem. You would have to find another cluster and hope it has a good module.
A common problem with the module seems to be with solder cracking around the main contacts. Have you checked the large solder pads for cracking around the contacts? It will look like a circular pattern in the solder. The pads can be reheated to reflow the solder and it only take a few seconds.