Ignition problems of the 1997 Ford Econoline

On April 12,2001 I experienced a loss of power and missing in the engine. Took the van to gulf coast Ford in crystal river ,FL . They ran a diagnostics on the vehicle and said tey could find nothing wrong. They told I should have the fuel system and gas filter serviced. The vehicle ran ok for the time being but on my trip to michigan the vehicle started the same problem again only much worse. I couldn't go any faster than 35 mph. This being a Saturday the dealers were closed in GA so I checked into a motel until Monday when I took it to team Ford in marietta, GA. They also ran a diagnostics and confirmed a cracked spark plug which they replaced and I had no further incidents back to michigan. My real problem is that I had purchased a service contract costing a $1,000 dollars and they told me that this is a normal maintainance problem. These two incidents cost me 211. 89 first time and 155. 02 the second time plus a 100. 00 dollar motel bill and two days of my time. I have written to Ford motor company in dearborn, mi 3 times and they have yet to answer any of my letters. At least they should have the courtesy to answer my letters. Why have a service contract if problems are dismissed as"normal".