Main things are to make sure you use thread lock on all screws that go into aluminium parts, seal your diffs up with grease or even better waterproof grease.
Build tips can also be found here:
http://www.team-durango.com/blog/?p=1017
http://www.team-durango.com/blog/?p=44
http://www.team-durango.com/blog/?p=24
Some good starting set ups for Uk outdoor tracks can be found here:
http://www.team-durango.com/blog/?p=869
Apart from that your good to go!
Hope this helps
Craig Collinson