Originally Posted by john_mayo
...My question is can I just replace the 200amp breaker and leave the rest of the electrical alone and it still pass codes? ...
Yes. All your equipment is grandfathered in. If it's in good condition inside, everything you've described sounds fine, except for the stab loc breakers. I've never heard of any issue with buss fuses. And IMHO, I'm much more concerned with wires that run inside houses, near combustables, than with wires that run underground or across masonry.
I agree with Stickboy, you must get other estimates, to bargain with, or just for your peace of mind. Just be honest and clear that they won't get the job and pay them for their time. In these hard times some people would rather make service call wages to write up an estimate, instead of sitting home and make nothing.