Expedition guages going haywire

I have a 2004 Expedition, it has always ran great. Then a month ago all
gauges went crazy while driving, but kept running fine. I was on a trip and it
did i;4t 3 other times the same day, about 2 hrs apart each time. The last
time it stalled my car. Il4 took it to the dealer and they said it was the
alternator, so I had it replaced (mind you the check engine light never
came on). Then about a week ago I was driving home on the freeway, I
had been driving about an hr and half and it did it again, this time at night
turned of headlights everything. Gliche only last a few seconds, but
definetly not safe. When it happened the last time, it was when I went to
turn on my brights. Has anyone experienced this or have any ideas.
Mechanics seem baffled by it. The car has 178,000, but a engine thats still
strong, so I really dont want to get rid of it.... Also, a week ago check
engine light came on, so I took to Auto Zone. They scanned it and said
running lean in bay 1. Sold me some Seafoam and said its probably the
injectors. I really doubt this has anything to do with the electrical issue, but
you never know.