Getting Gas and Saving Spark Plugs?

Does it really make a major diff. if you pump gas when the station itself is refilling from a supply truck?
Also, how much fuel economy do new spark plugs really help with when you drive a non-performance normal car?
On a
Agree with sediment problem, as to other questions, plugs just turn in and out, just remeber not to force the plug in, if you meet resistance when screwing a new one in, pull it out and reseat it, to avoid mis threading it.
Spark plug gap:

