some questions???
 

could my valve cover leaking/being cracked cause a vacuum leak?

and i think my powersteering box is going bad:( last night while i was leaving work, the wheel was real "chunky" feeling and felt like it was manual steering for about the first 30 seconds i drove it. then it went back to normal. what would cause that? the pump has the correct amount of fluid in it.

and how does the defroster hook up? i put in all the air ducts under the dash, and it blows out of the vents again, but not from the top of the dash, so my defroster doesnt work.

There is a vaccum line that operates the defrost flap if it is not getting vaccum it will not move the flap to direct air to defrost. That is all I can think of.

the the vacuum line in the engine compartment? on the upper part of the firewall??

Yes I think is comes in from the resovoir ball on firewall. It controls many functions of the ducts I think defrost and dash vents and the vents in the kick panel it comes in to the control unit in dash and then splits up I think.

On my truck there's a vacuum thingy on the firewall on the righthand side wich moves the flap for the defrost/heater outlets.It's near the heater box.It is controlled by vacuum,and moves when I go from airco to heater.When in airco position,it shuts the heater outlets.Maybe there's something wrong with yours,at least there was with mine.I removed the vacuumhose.I don't use the airco.
Hope this helps.

i didnt have it hooked up to a vacuum port.

thats what was wrong :)