The Sebring Haynes manual expands just a tiny bit on top of what those links show. It includes a few pictures, some torque values, etc..
To me, it seems like the timing belt part of this project is worse than the water pump.
I don't think you are supposed to re-use a timing belt under any circumstance, so your quote should include that.
$500 doesn't seem too bad. Water pumps range from $45 to $130+.... you want OEM (or better)quality here, in my opinion.
My Caravan is due for its timing belt/water pump replacement and I am trying to find a mechanic I trust and can afford. My family says I have broken all records for slowness regarding any repair....hour and a half oil change!!!!
This would be a late night/no sleep, all weekend, swear word producing project, I'm sure. Especially when one of those water pump bolts breaks off.