>>I am gathering as much information possible before bringing home our first snake (a milk snake). I haven't found much information about having a "feeding cage" as recommended by the pet store. Are they just trying to sell me another cage or is it really necessary? Also, if we use a feeding cage will it also need a heating pad? Last question, how long do we need to wait before transferring the snake back to its home cage after eating?
I don't think you need a separate feeding cage. They're probably trying to sell something. I keep an average of ten species in set-ups like these...

With large snakes I empty the large water jug and drop the food in. With smaller snakes, like the one shown, I put the food in the smaller container. The snakes go right in and find their food when they're ready. Doesn't take long for them to learn. They never have to leave the cage. Of course, I only keep one snake to a cage.
If I have more than one snake in a cage, I take them out, one at a time, feed, and put them back in their main cage. I rarely use heating pads with my snakes.
TC