Get your ordinary NGK and NGK spark plugs. ( 4cyl )
for 6cyl get the platnium plugs.

You sound a bit hesitant with helping him do the install.
If your not familiar with it or dont feel confident doing it. I would just take a step back and not do it.

One problem I usually encounter is removing the spark plugs. The sylicone thing that inserts into the spark plugs seems like it breaks off and I have to remove it with some long thin needle nose pliers.
To be on the safe side if you do help him just get a set of needle nose pliers just in case. Long ones that is.