Easy enough to do, just need a bit of patience, the ability to solder and a few bits from the scrappy/suitable donor.

All the wiring colours are as written in the Book of Blocks. Note the spellings are german eg GN is green and GR is grey.
Shopping list:
1x MID with plug and as much loom as you can get, at least 5".
1x Wiper stalk with buttons on end, plug and some loom. This should have 3 wires on it, BRWS/BRRT/BR or WS/RT/BR. (bear in mind estate and saloon are different and not all cars have a vaiable wiper delay fitted).
1x Coolant Bottle with Level Sensor and plug with some loom. This loom/plug might already be fitted to the car near the Brake Fluid Reservoir.
1x Washer Fluid Level Sensor/sealing ring ,some loom/plug. Again loom/plug might be lurking next to the washer Bottle.
1x Sump with Oil Level Sensor and plug and as much of this loom as possible.
1x Roll of 0.5mm
2 wire.
1x Book of Blocks for the wiring diags.
1. Identify all the wires on the MID loom.
2. Cross reference all the wires on the TID loom.
3. Dismantle both plugs, leaving the 'extra' wires in the MID Plug, and transfer all the common wiring to the MID plu. Be careful to ensure that the wires are fitted to the correct location on the MID Plug.
4. Connect Pin 6 on the MID to Pin 22 on the instrument cluster (ECU). GN.
5. Connect Pin 26 on the MID to Pin 20 on the instrument cluster (fuel gauge). BLSW.
6. Connect Pin 15 on the MID to the Brake Pedal Switch. SWGE.
7. Connect Pin 16 on the MID to Fuse 2 behind the Driverside Fusebox. SW.
8. Connect Pins 23 BRWS and 24 BRRT to the control stalk.
9. Connect Pin 27 on the MID to Pin 3 on the ECU Body loom plug. SWBR.
10. Connect Pin 20 to the Coolant Level Switch. BRBL. BR wire on plug to Earth.
11. Connect Pin 22 to the Washer Fluid Level Sensor. BRGE. BR wire on plug to Earth.
12. Connect Pin 13 to the Oil Level Sensor. BRGN. BR wire on plug to Earth.
The Washer Bottle has a rubber grommet in the middle of the engine side. Just pop this out and replace with the sealing ring then the sensor just slides in.
The Oil level Sensor is part of the Sump assembley, so plan to fit this as part of an oil change. Use the opportunity to clean the pick up strainer while you're there.
The Coolant Level Sensor is part of the Coolant Bottle.
Following the above you should have 3 wires left over: 1. MID Pin 17 WEGN Check Control.
2. MID Pin 18 SWGE Trailer Sensor, (check control?).
3. MID Pin 28 SWGR Stop Light, (check control?).
The MID will tell you to Check Headlight/Taillight every so often, but you should be doing that anyway
HTH, Al.