If you keep it as a tractor, your stock steering servo will be fine. A stronger servo for steering (Hitec645) if it were to be a dump trk or 6wd.
The old lighting system can be salvaged using this
Click it, use one for each switch.
The old sound system sounds virtually the same as the MFU. The MFU has alot less wiring, alot simpler wiring, but not the same wiring as old system. You can use a Servonaut sound & smoker, as it's a seperate entity from your lighting system.