Abs problems

Hello all.

So I thought my octy was bargain. I have replaced the wheel bearing. A ball joint.  A track rod end. 4 tyres. The CD player. The front speakers and then I realised I have no abs light. So I removed  the Speedo and it was obvious someone has taken it apart because the screws at either end are missing. I really need to decide how to tackle this. Assuming the dash has been broken to turn the abs light off, I was considering a second hand Speedo to see if the light then comes on, then fix whatever is making the light stay on. Help and advice welcome