Toyota Repair: RE; ABS ECU, abs light, diagnostic code

Question
I have a 1998 Sienna with 200,000 miles.  When outside temps and the van is warmed up, with no apparent reason the engine light pops on and the speedometer stops working.  It feels like the engine is not working as well, but that could be my imagination. If I pull over, shut the van off for a few seconds and turn it back on all is back to normal.  The dealer said I need to replace the ABS ECU.
Do you agree?
Does this affect the engine?
Is there an aftermarket store for this part, as I don't want to put an $1,800 part into this car.
thank you, Karl

Answer
At this point I don't agree, do you have the diagnostic code numbers when it was looked at by the dealer? An ABS malfunction does not affect the engine but if the check engine light comes on first it will turn the abs light on by default so it would really help to have some diagnostic codes at this time.