To run MS as I understand it you need:
Crank Position Sensor - either on a trigger wheel on the end of the crank, built in sensor a la AGG block, or from the dizzi
Manifold Absolute Pressure sender
Throttle position sensor - 2E onwards ran one, as did myriad other VAG motors - no need to buy Rovarse rubbish. You will be better going over to a single throttle butterfly (or ITBs) as the twin butterfly system on the 8V is difficult for a sensor to read from sensibly.
Note no airflow meter needed
How you run the ignition is dependent upon set up - wasted spark using Ford coilpacks, or keep the dizzi. Wasted spark will take you further if you start tuning and working on the engine - boost etc. This is why more people use it.
Your standard temperature senders should see you right.
The ECU kit and loom tails cost me £170 delivered plus VAT and ParcelForce's robbing charge.
Real world benefits? I'll tell you when my MS ECU (which is burning in at the moment) is on the car, maybe with a single throttle, maybe with the ITBs I have. This should be before the end of the year.
The key is that you can map on the fly and optimise the map specifically for your motor. As the complete set up is open source there are no programming charges, like you get on stuff like Emerald etc.
DannyP will be on in a bit. He has actual knowledge of MS set ups on VW stuff, so will be better placed to answer your questions.