I have a client who wants to remove a 3' wide window in a CMU wall and install a new 3080 door in its place. I'm assuming the block will be mostly hollow and also that the window already has a lintel in place above it. What is the simplest way to prepare the opening for the new door and frame, ie. do I need to fill all the adjacent cells, bucking, etc. First time I've tackled a project like this so any help would be greatly appreciated! Sorry if this has already been addressed in the past, but I am new to this forum. Thank you.