No, you shouldn't use the seals after they cut in the new seats bacause the guides for the cutter put a ton of wear on them. Also, the heat that the shop may use to pull out the old exhaust seat to replace it with the 3L one can damage the seals. For around $40 plus labor, it's a good investment against losing oil on a newly rebuilt engine.

http://www.bnmotorsports.com "And I will strike down upon thee with great vengeance and furious anger those who attempt to poison and destroy my CEG brothers. And you will know I am the Moderator when I lay my vengeance upon you."