hey guys, hopefully i posted this in the right area.

im looking to buy a diesel truck in the next couple months. Looking to spend under $15k.

I dont have a strong preference between a 99-2002 7.3 Powerstroke, 03+ duramax or 03+ cummins. i know each brand has their fanboys and they each have their strengths and weaknesses. ill probably decide on what to get when im ready to pull the trigger on the purchase and see what is available at the time. only requirements are 4x4 and crew/extended cab. I'm looking for dependable and reliable, not a 750hp smoke machine (which i think are super cool, but i dont need another money pit, we already have 2 rock crawlers). im going to be towing about 11k lbs for both crawlers and the trailer.

couple questions:

1.how many miles are too many miles? i have seen rigs with 250k still going strong and even 500k and still going strong.

2. auto or manual? ive heard manual gets better fuel economy but autos are definitely easier for towing. ive always preferred manuals, but interested to hear both sides.

3. where to buy from? lots of nicely priced diesels in TX, my dad bought a truck from texas and had it shipped out, it was an easy process and cost about $800. i also have friends and family there so id be okay flying out and driving it back. FL also has cheap trucks but thats pretty far away. I'm thinking i should avoid a lot of the midwest and northeast because of salt damage.

4. 3/4 ton or 1 ton? i dont really want DRW, but wondering how much of a difference it actually makes. i know that 1 ton will have a bigger rear end and heavier springs, etc. but have any of you bought a srw 3/4 ton and wished you had a srw 1 ton?

thanks guys