Just replaced the P trap under the sink in my '90 Westy.  I had the whole
kit from Van Cafe.  First, there was some discussion a week or so ago about
the length of the replacement hose shipped from Bus Depot.  It was said to
be 24 inches long, to short.  I measured the one I had, almost exactly three
feet (36 inches) and actually to long!  I reinstalled the original big bulky
hose because first there was nothing wrong with it and second I didn't like
the replacement.  Even though it would take up less room and might be routed
more out of the way it would have had at least one kink in the flexible
sections and I don't want that to trap 'stuff' that might get washed down
the drain.
And thanks for the tip some time back from someone on getting the old trap
off.  Use the Dremel!  Don't leave home without it.  There was no way the
old trap was going to unscrew, the whole fitting was turning in  the bottom
of the sink.  Couple of cuts with the Dremel and some prying with a big
screwdriver/pry bar/wrecking tool and it was apart.  BTW, had to replace for
two reasons.  First, the bracket inside that the screw that holds the bottom
half of the trap attaches to was broken and the screw itself had rusted
away.  In addition the stuff growing in the trap had plugged the drain to
the point that it didn't (drain that is).  So it might be a good idea to
unscrew that little screw on the bottom of your P trap and do some
cleaning.  Water stands in the bottom there and nasty stuff grows.