Walls and Ceilings - Wall to Ceiling joint

Hi, I am replacing a section of wallboard in an older house. The existing wall is 1/2 inch dry wall covered by 1/4 inch of what appears to be stucco and a thin layer of plaster. I am using 5/8 wallboard shimmed with door skin to build it up to the old wall. My question is how do I make the joint from new wall to old ceiling - It is a sprayed on textured ceiling. Should I use tape at the ceiling joint, how is this applied?
Also, should I relieve the edge of the old wall where it would join the new wall board in order to tape this seam. The house was built in the sixties. Any advice would be most appreciated.

Miles

You can caulk the seam between the wall and the ceiling. You can also put crown moulding up as well.