I know the SS was the main tool in carrying out the final solution, but what was the extent of the Wehrmacht's involvement in the systematic genocide.
They were complicit and helpful in the genocide. The first stage which was carried out by the Einsatzkommandos were in co-ordination with the army and followed just behind the front lines. German soldiers were often were witness to mass shootings even though they weren't supposed to be there. Certainly high level commanders were aware of the situation.
The 2nd stage with ghettos, trains and death camps was largely co-ordinated by the SS with little military involvement.