A quick question for the GM techs out there. The '04 Impala I got for a work car is turning out to be a pretty good car. Lots of little things that were allowed to accumulate have mostly been easy fixes. One troublesome issue has been the fuel gauge. When first started, it reads full. Within a few moments it drops to zero and the low fuel light comes on. Does this sound like an issue with the sending unit or the gauge itself? I've heard the GM dash clusters have problems but I don't want to pull it and get it rebuilt only to find that isn't the problem. I've accessed the fuel pump and did find a rodent gnawed wire. I fixed that and it didn't make any difference. I suspect the dash cluster but before I pull it, I want to make as certain as possible. On a related note, can I pull another one from the bone yard and swap in while I get mine rebuilt?