What are the common problems to look for on a 2004 Ford F250 7.3 liter

if you keep it serviced regularly,not much..my brother has an 01 crew cab with over 400,000 miles on it! he was going to put a fuel pump on it and the Diesel Mechanic that does all his work told him to throw that Airtex fuel pump in the trash can,cause he ain't putting it on his truck! he told him,"you've got AAA" if your pump quits i will get you one for cost where he works at the Ford Dealership! he works on em at home,for a fraction of the dealer labor rate.only thing i know he had done is replaced all 8 injectors @ bout $300.00 each! he's had it bout 10 years and we pull trailer after trailer of Christmas Trees from the NC mountains every year.he buys and sells at Auctions every week,5 days a week, pulling a trailer(heavy loads most of the time)..goes to flea market every Sat and Sun pulling a trailer full..been putting bout 1000 miles a week on it! keeps it clean and serviced..every weekend,someone wants to buy it,and some have thrown the cash at him(more cash than it's worth),but he won't sell it!