I notice you are in Bmore...is it convienent at all to get to Gaithersburg? I have no vested interest in DPS Tuning, other than getting great service there for my clutch job and timing belt job, at a great price.
To do the belt, idlers, tensioner, water pump, thermostat, and gaskets my TOTAL was right around $960. That is HALF what your dealer is asking for.
Not sure if you need a coolant flush? Since I had recently completed my 90k service, I believe DPS just dumped my coolant and reused it since it was good.
Anyways, if going to Gaithersburg is good for you, I suggest giving them a ring.