Yep its definitely difficult to slide on especially if the attachment has a lip of any sort.
Grab a rag and smear on some rp7/wd40. Works quite well.
Just don't go overboard as wd40 i'd imagine isn't too good for the oil.
Connecting it to the motor is difficult and you will end up feeling like your going to break your forearm pushing it on.
Cut the oil drain off so that its straight, thats what i ended up having to do as mine too was on an angle or does it angle from the start of the attachment? :S
That bit of hose I gave you was the softest stuff I found in that size. The gear I got from pirtek was very very solid.