Adding posts now, metabox later

I have a site I am switching to Wordpress, because unfortunately sometimes if you want something done right you have to do it yourself. I intend to use a custom post type, and I am not very familiar with Wordpress (or programming for that matter). So I have managed to implement the custom post type, but I now still have to understand how to add a metabox (in fact that is done too, but I have yet to get the saving metadata part working) but my other responsibilities are getting in the way, so I will probably not be able to learning and implementing a working metabox right away. What I want to do though, to get my site working again, would be to start posting content without the extra custom fields and add them later when I finally manage to implement the metabox. Would there be a problem with doing it like this (content now, custom fields later)? Would there be any difference between posts added before extra fields were implemented and those created after they were implemented? I am also asking because let’s say in the beginning I have 2 custom fields, and then I decide to add two more. Let’s say I have 5 posts in the first month with custom fields 1,2,3. After a month I realize I need two more custom fields (4 and 5). Will I be able to go back and add/edit data for the custom fields 4 and 5 for the older posts?