[rheavn]

You asked, "Does anyone have a diagram or can tell me where the dessicant air dryer filter is located?"

It is on the rear wall of the left rear wheel well.  Sits inside the tag tire.  Filter is mounted on top of the dryer.  You may have to raise the coach to see it.

You wrote, " I have a really greasy/oily looking canister at the rear in the engine compartment on the right of the engine with some big over 1" heavy hoses running in to it..."

I believe the filter you are referring to is mounted low on the right side by the frame rail and it is the hydraulic filter.

You asked, "oh yeah, where are all these drains referred to in the previous posts please?"

I'll assume you are referring to the air tank drains.  If so, on every air tank except one the petcock drains are located on the bottom in the middle of the tank.  The only tank that doesn't have the drain petcock in the middle is the rear crossmember air tank that sits over the transmission--it has two petcock drain holes.  One on the left and one on the right.  You cannot see all of your air tanks without being under the coach.  Reaching each petcock drain can also be challenging, but can be done.  If you don't find at least 10 air tanks you have not found them all.  Some coaches have an 11th tank in basement compartment R-1.

If you need to refresh yourself on where each tank is located, refer to posting #54 at the below link.

http://newellgurus.com/showthread.php?tid=1699&page=6