I don't know what sort of bed your model has, but I assume the main bed is a fold out couch. If your going to re-upholster it, then you might want to consider replacing the original foam with some sort of memory foam, perhaps with a dense base material. There are companies that will make custom cushions with high quality bedding material. I thought about doing this with ours, but as the upholstery was in decent shape, we opted to go with a memory foam topper. The advantage to having a custom cushion is that you don't have to fool with storing a topper, and you can have a thicker cushion as well.
Having a really good bed to sleep on at night is a high priority for most of us.