All valid points, and all a great collection of reasons to repair it. It's not a costly thing that will save you alot of hassle in the future, especially what rwenzing said about you only have one MIL, if it's on, it's on, and you don't know if anything else has gone wrong.
ALSO - If you replace the parts and the light is still on, even if you clear it (and it comes back on), give the truck some time. Drive it for a bit. Mine took about a week to stop showing up. It may not be the case with every Ranger but it's always a possibility. :)