I agree with the plug change. When I pulled the plugs on my Hemi truck they were had twice the gap they should and were at 90,000. That 100,000 mile change is way too long. You will be surprised at how much easier it will start and an increase in gas mileage when you swap new plugs in.

It is a bolt in deal like the crank sensor , bolts in the timing cover on the passenger side behind the thermostat.

Thank you