I fly through ORD every two weeks or so, so here is some info which may help.
Most United flights arrive at either B or C gates, which are in terminal 1. If you are arriving on a regional flight ie small plane, it may arrive at the F gates, and you will need to change terminals. (Columbus may well be arriving at an F gate)
Please go to united.com and use the 'check flight status' option to put in your city pairs. This will give you an idea of your gates. They WILL change on your flight date, however. (you should be able to determine though if your flight arrives at F or at B/C - this is important information)
I usually arrive/depart from a B or C gate. If you are going from B to C or vice versa, you will go down the escalator, along the dark colourful path designed by Disney I believe, and up the other escalator. This can take 10 minutes at a fairly brisk walk, depending on distance bwn gates.
If you are going from F to B/C, you can leave F but DON'T go through security - there is a little pathway to get to B/C. You could take the train, but by the time you exit, go down, go across, go up, take the train, go down, go across, go up etc etc etc it's pointless. You are best off walking - I usually walk anywhere I can at O'Hare as it's usually faster than the train.
TED flights all leave from a 'TED corral' which are at the far end of the B gates. Before you get to TED, you pass a McDonalds, Chili's, bagel place, Starbucks, hot dog place, and washrooms.
TED serves very good boxed selections for $5 - you can see them on the website. My personal favourite is the 'right bite' which includes hummus, pita chips, pseudo Ritz chips, Toblerone, etc etc etc. I point this out as your conneciton will not really allow you time to stop for a snack between flights, but you should be able to find a box which meets your needs on board your flight.
45 minutes for a connection will require some brisk walking, but you should be ok. Note that you may have delays at ORD due to weather; if your flight arrives late still try and hoof it over to your connection - it too may be delayed.