from my past experience, 700 sound about right for all of that work. in your original post you had said "timing belt" so we thought you were getting ripped off.

Unless the timing belt is making noise, you can go on without changing for some time but after 100k on the car, you just dont know when it might give up and leave you stranded on the road. then, you would have to pay for tow truck and deal with hassle.

the timing belt is not an engine issue my friend. just because it is located close to the engine does not mean it is an engine issue. this has nothing to do with the engine. they wont even touch your engine.