Seeing how you have already decided on scale, HO, and what you want to get out of it, Automation over prototyping and collecting rolling stock, there is still plenty for you to do. As mentioned DCC is a great way to start, converting all the existing engines requires adding circuit boards in each and rewiring the track. DCC is standard so in most cases you can pick and chose manufacture between the trains and the controllers you want to use. Then go with block detectors that will return a signal whenever a train is on a given section of track. For complete automation, and using open source you can go to JMRI, Java Model Railroad Interface, with that software you can start small by just using it to control your trains with your phone or web browser to complete automation by running the whole layout, starting, stopping, controlling switches, even turing on lights you may install in building on the layouts. This alone will keep you busy for many many hours.