where is the ECM located on an 88 Deville?

[helplessCadguy]

This is my wifes car,I have owned nothing but Mopar for 40 years so I need a bit of help. The car had starting to act up by starting when it wanted to and sometimes not. When it would start it would surge as it went down the road. My first guess is the ECM, so I got a new one on Ebay. I dont have a factory service manual so I dont know where the ECM is hidden at. The ecm was new in the box and it mentions changing a MEM-CAL chip from the old ECM to the new ECM. Is this to keep the mileage the same? Does this new ECM need to be programmed at the dealer first or can I just put it in? Any hints as to other things I should check? Lastly,how does the sequence to get the codes work?
PS<I notice an awful lot of peoples calls for help on here go unanswered,please dont be shy and assume someone else will answer these questions if you know the answer. I am a disabled vet on VA disability so I cannot afford to take this car to a Cad mechanic,so any and all help greatly appreciated.
helplessCadguy
(really helpless Mopar guy) LOL

 

[Ghost C]

The ECM is located inside the dash, remove the right hand side sound insulator panel from underneath the dash board. Yes, you will have to switch the chip from the old ECM to the new, as this stores all the information from the vehicle, and the new ECM will not work without it.