Central American Missions Work

After spending almost 2 months in Costa Rica this past summer, I am interested in taking a trip back sometime in 2009. The idea is to take about 3 months total, spending a few weeks in the middle in Costa Rica and the rest of the time split between driving there and back. There will be about 4 of us, with our gear and missions supplies in the vehicle.

The idea now is to get an older (1990-2001) Land Rover Disco because of its capabilities, high clearance and 4x4, among other things.

My question is have any of you gone on a similar trip, or does anyone have tips, ideas, or critiques about these seedlings of plans for this trip.

Any help is appreciated.