Is dish going to redeem the OTA coupons?
Of course! They built the TR-40 specifically to get new customers via the coupons, and possibly upsell them on Dish Network programming, or a TR-50, or both.
how do I hook rabbit ears into the dish box?
From the looks of the back of the thing, you'll need a cable-style adapter. Rabbit ears typically have 300 Ohm twinlead coming out, and you'll need an adapter for 75 Ohm coax. These are extremely cheap, and often come with TVs for no extra cost. You probably have 5-10 lying about from a lifetime of TV purchases.
How would I switch from dish to OTA channels?
Two ways are possible. If your TV has AV inputs, then hook your satellite receiver to one AV input, and the TR-40 to another and use the built-in switch. If you don't mind the loss of quality using the RF inputs/outputs, then hook the antenna to your TR-40, and use it's RF output going to your satellite receiver's RF input. (Yes, most Dish receivers, particularly older ones, have this for passthrough.) So, if the satellite receiver is on, your TV sees it. If the satellite receiver is off, then your TV sees the TR-40. VCRs used to be hooked up this way before DVRs made them obsolete.