I had to replace the leaking vent lines on my 87 Westy this fall so
heeding all the cautionary tales on the Internet I replaced the whole
works. For me the tank part did not seem as hard as I expected, the main
lines were straight forward but the two three way connections on the top
of the motor were tough. Very hard to get an angle to push on and the
connectors seem bigger than the rest. In the end I used Vaseline which
helped. If you do it yourself take your time and take special care not
to get any dirt in the lines (the injectors are very small!!)
http://www.benplace.com/fuel_line.htm    This website is an excellent
description on how to replace fuel lines in the engine compartment. It
looks confusing to start with but really becomes clear when you are
actually doing it.
Gerry
87 Westy