I have a new sump gasket and all the parts to reseal the turbo drain tube. Should I use a sealant on the sump gasket an if yes what sealant. I also ordered a block heater kit. I should have looked to see if my car has one already. I know it doesn't have the wiring, but did they come with the heater installed?

title line should read

sump gasket 300TD 1984

There are two schools of thought on this, one puts sealant on anything they can to cover themselves in the quality or lack of in thier work, or the other who are more restraint.

Provided, the surfaces are cleaned and dry, I would suggest a quick drying agent to bond the gasket on surface so that the gasket does not move when offering the sump to the block.

If you have doubts, use only a thin bead to apply on both sides, remember, when the sump compresss on, the sealant will squeaze out wards. Use a thin film only. Tighten the sump screws evenly, and cross tighten the screws.