repair shop (geht es hier um die früheren RAW's?)

Instandhaltung tends to cover both areas - repairs and maintenance. The secret of success is spotting the need for (pending or future) repair during maintenance! E.g. On large construction projects the mechanics are often paid rate X when plant/equipment is in service or in maintenance. Should it break down and need repair during service they are then paid X - Y, a considerably lower rate!!

is another option, as would be "maintenance company" or "maintenance provider" (for buildings etc.).
So much depends on the context with this one.