Strange Problem with 1999 Town & Country

I have what seems to be serious problem with 1999 Town
and Country: all of a sudden it seems to have stuck
on a middle shift and automatic transmission doesn't
seem to shift as you accelerate - seems as if
something wrong with transmission. And together with
that "Service Engine Soon" lighted up and what is
particularly strange speedometer and mileage counter
stopped working.
I'm at a loss what could it be. If it is transmission
breakdown, then why is speedometer is at zero no matter
what speed you drive.. Or could it be that some
electronic component controlling all of those parts
broke down?

Any advice will be greatly appreciated.

IP.