Comcast thinks the answer to your question about not being able to use the Guide is to tell you to use the Guide. This a capability they dropped from the box and remote years ago. What your father may be able to handle better is to right arrow to get the Mini Guide which will show Favorites if you have Favorites set as your default guide. The TV picture remains in view next to the Mini Guide so there's less chance of getting lost.
10 month old / marked "Answered" dead thread now being closed.