Note:  I searched through posts for about 15 minutes and couldn't find anything about the problems I'm having.  Here it goes...

Year: 1997
Model: Sidekick 1.8L 4x4
Mileage: 145,000
Check engine codes: P0340 and P0420
Inspection expires: April!  (please help!)

Code P0420 - "Catalyst efficiency below threshold":
- Check engine light has been on a while with this but I haven't worried about it too much since it's just emissions.
- I've been told it's a catalytic converter that might need replacing.  Any suggestions?  I've heard replacing the converter can be really pricey.  Could it be anything else like an O2 sensor?

Code P0340 - "Camshaft position sensor circuit malfunction":
- This is a new code that I've known about for < 1 month. 
- I'm shocked that this code showed up because I had a mechanic replace my camshaft position sensor recently (January).  My car was dying on me, then wouldn't start for 30 minutes.  I haven't had issues with the car dying since he replaced the sensor, but now the there's a code for the sensor?

I'm open to a lot of different options.  Any help with either problem would be really appreciated.  I'm hoping to give the car to my little sister in a few years when she starts driving.  And I want it to still be running!

Thanks!
Robert W. Berry

The first one sounds like the cat needs to be replaced, the second one?
could it be an old code not cleared? or how about going to the mechanic
and having it warranted since it's only been a short while

Wild