Buy the parts and do it myself

My friend says her mechanic states the trouble codes for a catalytic converter for her car. She's already replaced it and is hundreds in the hole for now. How often does this happen with new cars? I have a '92 Camry with the same converter and only the EGR has been replaced... Anything to be concerned with?

just change my fuel pump and filter because
car was shutting off both on idle
and driving,nothing has change since,
it still does the same,though has gotten
a little better but on acceleration while
doing a drive test it seems to jerk for
a few seconds while holding the pedal then releases,this is at 3,000 rpm reading. the car has no problems starting,been starting it everyday and just driving around my resident area.
the shutting off only occured once but the jerking thing continues at 3,000 rpm on acceleration but it does releases
and the car continues to drive normally.
nothing technical as i know,whats causing this.

Car will start and run fine but no matter what gear you put it in (p,r,n,d4,d3,2,or 1) it want go anywhere and when you put it in reverse and hit the gas it tries to move forward just a little, will sometimes do it in park, any help would be nice. I have already changed the soleniod on the trans

i bought finders and lights for my 94 and they dont match i have a gap between the lights and finder whys that

Where can I go to get this fixed and how much would this cost?

Plastic cam plug seal has been replaced twice already because that's where the oil was thought to be coming from. However, this 3rd time, gasket maker was used to help it seal more. Ive recently checked around the cam plug seal and it is dry and not showing any signs that it's leaking from there but I'm still getting a small pool of oil under the area of the cam plug seal.

Also, at night lights in the transmission selector. IE D/R does not light up.

What would cause that