2002 VW Jetta 2.0L - Disintegrated Spark Plugs, Rough Idle after Replace

Hi everyone, newbie here with a couple questions!
So, yesterday I was driving from Ottawa to Kingston, and about halfway through the trip I started to get really sluggish response from my car. It felt almost as if it was trying to make it up a hill with a heavy load. I pulled over and the idle was rough, but we were only a few KMs from home so we kept going to try to take a look when we got back.
I took it into Midas today, and they replaced the spark plugs and wires. The old spark plugs had worn on two cylinders so bad they didn't have the electrodes anymore, it was worn almost flat. So this of course had to be done.
After replacing them, the car has gained some power back, but still runs rough, lacking power (but not as bad as before) and idles rough. The rough idle has a pattern of it being bad, then worse, then bad, then worse, which can be timed to a regular pattern (hope that makes sense).
The shop is closed on Sunday, so I will be taking it back in on Monday to have a more thorough look.
My main questions are:
1. What kind of damage could a worn out spark plug do to the engine?
2. How likely is it that a valve issue has developed, meaning big $$ to repair?
3. How much should I expect for a valve repair in Ontario?
4. Is there anything I could look into in my driveway while I wait for the shop to open?
I've heard similar issues be attributed to MAF sensors, O2 sensors, vacuum issues, fuel pumps...
I just don't want to have all these issues fixed, then find out the real issue is a $2000 job that I would scrap the car for.
Thanks!
So, yesterday I was driving from Ottawa to Kingston, and about halfway through the trip I started to get really sluggish response from my car. It felt almost as if it was trying to make it up a hill with a heavy load. I pulled over and the idle was rough, but we were only a few KMs from home so we kept going to try to take a look when we got back.
I took it into Midas today, and they replaced the spark plugs and wires. The old spark plugs had worn on two cylinders so bad they didn't have the electrodes anymore, it was worn almost flat. So this of course had to be done.
After replacing them, the car has gained some power back, but still runs rough, lacking power (but not as bad as before) and idles rough. The rough idle has a pattern of it being bad, then worse, then bad, then worse, which can be timed to a regular pattern (hope that makes sense).
The shop is closed on Sunday, so I will be taking it back in on Monday to have a more thorough look.
My main questions are:
1. What kind of damage could a worn out spark plug do to the engine?
2. How likely is it that a valve issue has developed, meaning big $$ to repair?
3. How much should I expect for a valve repair in Ontario?
4. Is there anything I could look into in my driveway while I wait for the shop to open?
I've heard similar issues be attributed to MAF sensors, O2 sensors, vacuum issues, fuel pumps...
I just don't want to have all these issues fixed, then find out the real issue is a $2000 job that I would scrap the car for.
Thanks!
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