It is very hard to wash pots and pans so I want to convert my 33" double sink into a deeper single sink (9 inches). I have a limited budget so I wanted to know if my plumber is going to charge me a lot of money for this? Currently I have a disposal on 1 side and a drain on the other. Is this difficult and costly to do?

Hard to say. The actuall plumbing hook up should be fairly easy and quick for a plumber. But there are a lot of factors in changing a sink. Are you buying the sink from the plumber? Is the new sink going to fit exactly in the old sink location(without altering counter top)? Are you installing a new faucet on the new sink, or using the old faucet? Are you keeping the gargage disposal.

I'm replacing the sink and faucet. I still haven't decided whether I should replace the disposal. Thanks!!

As long as you get a sink that will drop right in the old location, I don't see the plumbing side of it being to bad, maybe even something you could do yourself, but if you feel more comfortable with a plumber, they should make quick work of it. Good luck and please let us know how things work out.