a few questions about my 1983 300sd

hi everyone. i recently got a 1983 300sd with 183,000 miles on it. i have a bunch of questions because a bunch of little things need to be fixed, but maybe i'll only get into a few things now.

first- is there anywhere to get a parts number list for this car? perhaps with a diagram, so that i can see what needs replacing and then just note the part number? because i don't have anything like this and i only know so many technical names for parts, i have to describe the parts the best i can.

the black plastic elbow tube that connects to where the air filter is (this tube is probably about 3" in diameter, its not a little tube)- it has a crack in it. it needs to be replaced. the engine raddles a bit when its idling because of this. once given any gas, it stops immediately because there is enough suction to pull the crack closed. anyway, i don't know what the part number is or what that piece of plactic tubing is called- can anyone help??

i have never owned a diesel car before, but i am concerned about the spots the car leaves on the driveway after being parked for a bit. there is a little bit of oil, but it seems like fuel is leaking too? it is not oil- and when i bend down to smell it- it smells like diesel fuel- but that may just be coincidence. but whatever that is, it is leaking much more than the little spot of oil the car leaves. i really don't think it has an oil leak. its this other stuff that concerns me. maybe this is normal for a diesel car, but i wouldn't know- i've only had this one for a few weeks. any ideas? could these two problems (if the second is a problem) be related?

other things that need attention are:
cruise control doens't work
power locks don't work (previous owner cut(?) line [in trunk])
both driver and passenger seat don't move up and down- power seats work fine every other way. you can hear the motor when you push the lever to have the seat move up or down- but the seats don't move.
vacuum modulator needs adjusting (sticking 2nd gear)

i have no idea how much any of this stuff costs to fix. maybe the problems are being caused by something small- but i wouldn't really know.

thanks for all the help regarding the things i mentioned.

nick