I am new to tuning and much of this language is, although somewhat familiar (engineer by trade), very foreign in this context.  I am wanting to convert my 2001 Audi S8 from auto to manual 6 speed.  This configuration was offered in Europe but they used a different engine code.  I talked to some people and they gave me some tips on what ECU's should work for the swap but they are a different engine code.  He lined up the emmissions and motronics versions (ME7.1.1).  Some of the issues I'm trying to correct with an ECU swap are: cluster programming (i've heard that the cluster won't program to the manual code unless a manual ecu is present?), cruise control functions, idle adjust due to no torque converter, allowing for the TCM to be removed, eliminating the abs light, potential check engine lights and ESP light. I have my stock bin file and the one from the recommended ECU with a different engine code but I have some questions.

Does this sound correct that most of the issues with the manual swap could be caused by the incorrect ECU?

Could there be any major issues using the incorrect engine code's ECU file or physical ECU?

Would I get exactly the same results by flashing my ECU with the manual file?

What is all stored on the ECU other than the maps that people here are usually tuning?

I'm sorry these sound like novice questions but I'm having a very difficult time finding a used ecu with the part number I need and new ones are about $1500 so I'd like to try and flash my ECU with either the manual file or a modified version of mine original file with some modifications taken from the manual file.  Where do I start?  How much risk is there to brick my ECU?

Another thing to take note of is the immobilizer. If you buy a euro ecu the immobilizer won't match (if your car has one at all). Make a backup of your 95040 before attempting to flash anything.