NOt sure what you are trying to fix in the fuel sending unit. It is very easy to open and you should not have a problem. I assume you have been able to remove it from the tank. I used a big pair of channel locks and I was able to unsrew it. Make sure you have a plastic tub or other device handy so you don't spill any fuel in the car.
Look on the bottom of the aluminum tube. There is a little nut encased in a plastic cup. Using needle nose pliers, get a good hold and unscrew the nut. WHen it is loose, use your fingers and remove the nut, aluminum cap and plastic washer and carefully remove the tube. It has two very delicate resistance wires that the float runs on. If they are broken, it is best to get a new/used one that is not broken. I have not had succes soldering them back in place. NOt much to solder anyway. Could be you have gunk buildup and it is gumming up the works. Just be careful and do not break the wires like I did.

Good luck.
Henry

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