Cadillac Repair: Cadillac northstar seville 1993, cadillac northstar, car leaks

Question
I just sent my 1993 caddilac seville to the dealer for overheating problems.  Although I had noticed the car leaking coolant the car only overheated once and I only drove it to the dealership (about 2 miles) since then.

The person from the dealership calls and says that the water pump is screwed and will cost 407.00 to fix it.  But the main problem is that he cant check the engine because the car leaks coolant faster than he can get in there.  

I know little about cars and just want to know (1) I am getting a fair price at $407 to repair a water pump.  (2)What are the chances that this is just the beginning of something much larger such as head gaskets?  (3) If someone knows how/where to get Cadillac parts cheap so that I can just pay labor costs.

Answer
FIRST off the dealership will NOT allow you to bring in your own parts for them to put on the vehicle.

Would you go buy your bacon and eggs at the grocery store and take them into a diner and ask then to cook them for you ?????????

You have to get the engine running FIRST before you can determine any other damage.

$401.00 is about right for a water pump.