I have a 98 f-150 with 4.6 V-8 with 61500 miles. A couple of weeks ago while towing a boat up a slight grade I got a violent shudder while the truck was up shifting in the 40 to 50 mph range. The check engine light came on so I pulled off, shut off the engine and restarted it. The engine light stayed on for a day or so and then shut off as the manual states it would if there were no problems. For the next week I felt what I thought was the transmission dropping out of gear a couple of times for a second or two and very randomly so I took it into a Ford dealership for service. They overhauled the valve body and did a tune up. They claimed to replace the plugs, fuel, oil and air filters along with cleaning the throttle body. I've had it 6 days now and it has been stalling on me both when I'm backing out of a parking lot and when I'm on the freeway. Then yesterday it just would not start period. I unhooked the battery for five minutes and it did finally start after a lot of cranking. On the way home it died twice again.
I'm now thinking what I felt while towing up that grade was the engine stalling out and not a transmission problem. I have checked the fuel filter and it is new. I don't know how to check the throttle body to see if they in fact did clean it. Any thoughts on this problem before I take it back to ford. The service guy there seems like a bullsh*#ter and I would like to recommend to them what I'd like them to check so they don't bleed my bank account dry.

Thanks
Blaine