There are so many possibilities, that I could go on for ages.
I will try to make this as simple for you as I possibly can.
Start with the spark plugs.
When was the last time they were changed?
Might be time for a new set.
The high idle can just simply be temperature related.
What has the weather been like lately?
What is the idle speed when the coolant gauge is in its normal position near the center of the gauge?
The idle speed can also be caused by a loose connection between the throttle body, and the intake manifold, or between the intake manifold and the cylinder head, or a loose vacuum hose that attaches to the intake manifold or the throttle body. It takes a bit of effort to hunt down this type of issue.
Or it could be that the Mass Air Flow sensor is starting to fail.
But here's something you and your husband can try in the mean time to see if it helps:
1) Drive the car to "warm up" temperature.
2) Ensure any battery draining devices are off. Ie. headlights, interior dome lights, HVAC, stereo.
3) Turn the car ignition key to "OFF"
4) Wait ten seconds
5) Turn the key to "ON" (not start)
6) Wait three seconds.
7) Perform the following five times in five seconds or less. Fully press the gas pedal and release.
8) Wait seven seconds from last of the five releases.
9) Fully press the gas pedal and hold down. Within ten seconds the "Service Engine Soon" light should begin to blink.
10) Wait another ten seconds (while still holding the gas pedal) and the "Service Engine Soon" light should stop blinking.
11) As soon as it stops blinking, release the pedal, start the car and check the idle (should still be around 700 rpm)
12) Let the car idle at 700 rpm or so for about 25 seconds, rev the engine a few times and then let it return to idle.
13) Shut the car down.
You car has now relearned the new air volume, which should be different than it was (stock). You may notice a bit of a rough idle for the next 20 miles. This is normal and will go away. The reason you should make sure idle is around 700 rpm (full warm up) is because the car measures the air curve in relation to idle, so you don't want to confuse it.
Give that a try and see if it helps.