Do you know of any major problems with 2006 Foed F350 Diesel I am getting ready to buy one with 125,00 miles on it

Very good truck. Have a qualified diesel mechanic check the engine (especially the turbo) and transmission. Look at all maintenance records. If you buy it, change all fluids--engine oil and filter (only use full-synthetic diesel HDEO), brake fluid, transmission fluid and filter, coolant (50/50 proper antifreeze/distilled water/SCA), differential fluid, power steering fluid, and transfer case. Also, grease the ball joints and steering with NGLI #2 synthetic grease with moly (Valvoline SynPower), change the air filter, and change the fuel filter. After you do all of these things, you'll know where you stand.