I am thinking about buying 95-99 Deville with head gasket problem. I called dealership and they said 3000, engine has to be removed and headbolts replaced with bigger bolts and new tread has to be cut.
Here are some questions:
Can gaskets be replaced w/o removing engine?
How much are bolts and retreading tools (kits)?
How much parts will cost me?
How long does it take to remove engine, it seems to me it is going down with subframe and transmission? So I disconnect everything and just lift front of car?
Thanks.

You're going to have to take out the engine to replace the headgasket. My mechanic says a headgasket replacement costs $1500 because the engine has to be dropped to do it. The headgasket alone cost $20, the kitsI'm not too sure about but shouldn't be too much neither. Here's how its done:
http://www.cadillacforum.com/m_9528/tm.htm

Head gasket replacement in the car is not recommended, parts can run up to 500.00. worst case you will need new engine. time sert kit runs 350.+.Tools required allow additional 125.00.