First of all, you can access Micrologix through an OPC server(for an industrial application) only by using RSLinx Classic or Matrikon OPC server(the first solution is cheaper). If you want to connect the Micrologix to other devices that are Allen Bradley, you don't need an OPC Server.
Of course there are some questions regarding the project, to see if it's possible what you want: type of network used(Eth/IP, DNET), where would you like to use the data, at which refresh rate, etc.
I work for a company that is a System Integrator for Rockwell products so I have access to their knowledgebase, and experience using these software.
For any questions regarding the project, please do not hesitate to contact me.