If you choose not to do so, don't be upset if your blocks are not accepted into the swap. It is not up to the hostess to police you every step of the way. Your hostess has spent a lot of time planning the swap and she expects everyone to comply with the guidelines. They are not open to individual interpretation. There are no such things as silly questions.
Computers are prone to crashes and errors.
A hard copy will save you much time and frustration. Please respect the due date she has set. Know where you are mailing to and make sure you mail your blocks in time to reach their destination. Some hostesses use them and some don't. I don't usually designate a signup deadline but request that all interested people, notify me so I can put them on an update list.