for your CEL LED you have to have the ignition in the "on" position (but you don't have to have the car running) With the key in the "on" position hold the buttton down for 3-4 sec to read the codes and 8-10 to reset the CEL.

BTW where in iowa do you live?
I use 5w30 winter and 10w30 summer here in MN and WI, some ppl prefer heavier weight during the summer like SAE30 or SAE40 as well as 0W30 and 0W40 synthetics. Everyone has their own opinion on what oil and what weight so its really up to you.

http://www.chris-longhurst.com/carbibles/index.html?menu.html&engineoil_bible.html