2003 Chrysler Town and Country

I have a 2003 Chrysler Town and Country that started stalling on me the
other day initially while i was at a red light and then twice while driving it
minutes later. The 3rd time the van stalled, it wouldn't crank back up. When
the key is turned to the on position, the engine and oil light stays lit. When I
try to crank it, nothing happens. There's no noise, no clicking like it's trying
to turn over, nothing. However, the battery appears to be just fine with a
healthy charge since after that i waited for 3 hours for a tow truck keeping a
cell phone charge and hazard lights on with no diminishing of battery
power. Before this, there was no indication in driving the van that there was
any issue. In fact I drove 72 miles that morning with no issues and a full
tank of gas and the return trip was when it suddenly gave me those fits.
Any suggestions on what may be causing this? The mechanic is trying to
say my computer is bad and they can't even begin to diagnose what the
issue is until I pay $760 before tax on a new computer for it before they can
fix the issue.  Which may be the case, but 3 months ago I had the
computer plugged into a diagnostic machine and it didn't indicate any
issues with the computer being faulty at all. Any suggestions?