Wow - bummer! Sorry to hear the diagnosis. Yours appears to be in advanced stage of illness, relative to mine. Anyway, I recently called the dealer and was told the front main seal is ~3 hours labor, including removing the radiator. I was told (by a friend) the head gasket is 6-8 hours if done by someone with a clue, otherwise I guess it could be more like 10. My dealer's labor rate for "B" labor is $106/hr. So the labor you quote sounds a tad high, but not ridiculous. (Anyone else care to comment?)
I don't know about the tranny stuff, but if it's the front pump seal, the tranny needs to come out. You may want to replace the pump itself, I've heard that a new seal on the old pump doesn't work well because the shaft wears or something, the proper fix is a new pump (and seal). The pump would tack on another few hundred $$$.
As to what else to change while the head is off, unless they've been done in the last ~5 years or ~50kmi:
1- Injection pump vacuum shutoff valve ($20-30)
2- All 6 glow plugs (~$75-100)
3- Closely inspect the serpentine belt tensioner ass'y ($25-250)
4- Have all 12 valve lifters inspected for wear (~$20 each)
5- Have the timing chain inspected for wear/stretch ($???)
The BenzBin lists the head for $1495, the trans pump for $265, valve lifters for $16/ea, and the timing chain for $62. Rusty will usually at least meet their price, if not beat it - and his service is reportedly superior to BB.
MegaParts has the transmission pump for $235, but their prices were higher on the other stuff.
Good luck, and keep us posted!
1987 300D - 229kmi
1987 300D - 234kmi
1984 300D - 206kmi