Front suspension. If it hasn't been taken care of expect to drop lots of money into it. Just the nature of the cheBy IFS. It wears out.
Not many problems with those engines I've seen. They eat EGR's, coolers plug. An occasional head gasket, but that year got the "second design" head bolts.
CP3's are rare but do happen, injectors start getting higher return rates. HOWEVER most of the time guys only find out about this once you tow heavy a long distance. When you're really working the engine. Normal day to day driving they never notice it. I usually have a large influx of high pressure side failures here when guys start towing their big trailers up north.
Water pumps, those are common on all year DurkaMAX's. They happen, easy and quick to fix, price isn't horrible.
Trim, HVAC actuators and bent doors. Window regulators. Cluster failures. Easy fix, but not cheap.
Engine mounts and trans mount. Not expensive but a decent task to replace unless you have a hoist.
Look at the electric pass threw on the Allison (passenger side) if the wires coming out are wet, you'll need to fix that and the internal harness, VERY common.
Hydrobooster and lines, they leak. Easy repair, but not cheap.
How willing is the owner to let you fully inspect it? Or better yet call a local shop for a full inspection. You pay the fee, or split with the owner. I'm really not sure of your mechanical ability (I mean absolutely NO offence with that), but I'd hate to see you drop the coin on a roach for overlooking some expensive parts.
I'm not sure about your auto cal question. BUT! If you can access a good scanner, get the engine at operating temp, control full line pressure at idle, look at injector return rates and actual vs. Desired rail pressure.
I only see the broken one's. Let's face it, a customer in my line of business never stops by to say " my truck is running great and every thing is A Okay."
With everything up ^there^ I wouldn't hesitate to give the truck a throw checkout and plop some money on the table. 250k I've seen much more than that, biggest I've ever seen was 440k and remember I work in a dealership, most people with those miles shy away from me.
