There really aren't any weak links in the 400. The subframe will only be a problem if you carry a lot of weight back there over really rough terrain over extended periods, but it won't hurt to have a spare in your possession. Just keep everything lubed. You might want to pick up spare clutch and throttle cables and pre-route them and zip-tie them in place, just in case.
"It's strange to have a creation out there - a deeply mutated version of yourself, running loose and screwing everything up. I wonder if this is how parents feel." -Dexter