EGR Valve cause of engine seizing?

I have 99 Navigator, I was driving this on the highway, when the engine just stopped, with no noise whatsoever, then the "check engine" light came on. I took this to a lincoln dealership (same dealership I have always taken it to, when I see or hear any noise. For quite some time the "check engine" light was on, I would take it in and they would tell me they can't find anything. Then down the road or a week later it would come back on. this problem happened several times in the past year. ) This suv was towed to the dealership when engine seized, they told me the oil may have been low. I towed it elsewhere and they could not find anything.
I have then towed it to GoodYear, they replaced the engine $$ and then found that the EGR Valve was in bad shape and of course it was replaced for 170.00. He told me that the dealership should have paid for this engine and in fact should have found the valve problem and corrected it. Has anyone heard of this? Is it true? I contacted the dealership and the service guy said that the engine would have been on constantly, not on and off.
Thanks for any suggestions. Single mother of twins.

I had a new 1997 Ford F-150 5.4L and the 5W30 oil was to thin and the engine would start go to 800rpm and it took about 30 seconds before I got pressure. The oil pump had a hard time getting suction.
I did the first change at 1000 miles and the second at 4000 miles I then went to thicker oil. I ran it for 98,000 mile and never added oil between changes before I totalled it. Definately use at least 10W30 oil. Ford always has excuses to avoid replacing an engine.
I really doubt both places claims.
I would get all bills from both places and take them to small claims court.