F250 diesel vs gas, 2wd vs 4wd, good used years

[Lego]

Hi! I'm so overwhelmed with information after reading these threads! Thanks for all that information!

I'm considering purchasing an F250 to haul my 2 horses and my agility equipment (about 5-7k lbs) about 50-200 miles each trip. I'm in Los Angeles in desert conditions and in the mountains (2k -5k altitude) and snowy mountain roads requiring chains.

I'm looking for safe, strong, reliable, low cost maintenance and hopefully some fuel economy. I will be moving to Ohio this fall or next Spring so my truck needs to be happy in Ohio conditions moreso than Cali.

I'm also looking into the possibility of Biodiesel but the research and information is hard to find (at least for me).

I love the manual trannys and I drive conservatively.

Do I want 2wd or 4wd? Gas or diesel? Any used years better than others? Any comments on major repairs/maintenance items to be expected at any certain mileages?
Is 94k miles ok for a '99 F250 Supercab 5.4L gas?

Any advice would be AWESOME!

Thanks.