A few bits of advice:
1) In your contract, be certain to spell out how deep you want the main
stump ground, how far out you want roots chased, and how deep you
want the roots to be ground. This avoids disputes after the work is done.
I forced one "tree expert" to grind a stump and roots 3 times until it was
done correctly. That's one advantage of COD - he doesn't get paid until
it's done correctly. (The first time, he went down 2" - just enough to hide
the stump after he kicked dirt on top of it)
2) How fussy are you about your lawn? Roots which aren't removed will
produce big crops of mushrooms for many years to come. The roots
decompose and produce perfect food for mushrooms.
3) As another poster has commented, stones will fly and can break windows,
dent siding, damage cars, etc. I'm always amazed that the guys who do
this for a living seem to be unaware of this. The grinder should be aimed
to toss stones in a safe direction and/or a barrier should be used.
4) The contractor should be responsible for all collateral damage. Ask
to see his insurance and don't hire him unless he has a current policy.
Phone the insurer to verify that coverage is up-to-date.
5) Get the utility companies to come out and mark all of your underground
drops. This should be free. Now there is no excuse for damage to utilities.
6) Get more estimates. The person you are dealing with sounds as if he
could be playing CYA.