Erratic fuel level indication

1st question: When if fuel up my 05 Buick Terraza, I get a low fuel light and the gage says empty. After about 48 hours and several start-ups etc, the indicator finally settles down and reads normally.....until I fuel up again. While it is "acting up" I also get the engine icon lit up on the instrument panel and, as one might expect, the "Average Fuel Ecomomy" and "Range" readouts are wackko too. Is this most likely the fuel guage sending unit?

Also, I don't know if I have On-Bd Diagnostics or not....the owner's manual says nothing about it....probably the "Helms" type shop manual would tell me about all that + the error codes and I reckon I should go ahead and spring for the manual. This make/model car has a terrible reputation, but I have actually been very pleased with mine...well, at least for the first 50K miles.....and it sure "ain't my first rodeo" :-) ..... so the $ spent on a shop manual would probably be well worth it (one stop at my frienly Buick dealer for a repair would probably pay for it.......and then some.)

Add'l question: I found that this sending unit is available at gmpartsdirect.com. at considerable savings. Has the newsgroup feedback (if any) re this firm been good?

Thanks in advance, Ed in TX