OK, about 80k on this car, and other than the notorius elantra
headlight issues, this is the first problem i've had... It will rev
itself, especially when I come to a complete stop, sometimes
intermittently when at rest, anywhere from 1100 rpm all the way to 3000
rpm-- a tap of the accelerator usually straightens it out...

what does everyone think? O2 sensor? If so, how do I change it? I'm not
an automotive idiot, just don't get under the hood of newer vehicles
often (I have 3 ice cream trucks, all 70's era chevy panel trucks)---
but I need to get the Hyundai running right, and want to do it as
cheaply as possible...

Thanks in advance folks.