It is (frustratingly!) amazing how quickly and sharply your technical skills advance when grinding away at comic pages. Keep that in mind before you jump into reworking early pages. It sounds like you're simply reformatting, not working any new artwork and in that case, I think it's best to take it slow but keep updating.
On the other hand, if you're going to be creating new art...
Updating old pages can be a vicious cycle of constantly "rebooting" the first couple of chapters in order to best reflect the current standard of work. Best not get too caught up on the refresh there unless this is a personal goal and/or an undertaking you're capable of calling "finished" when you reach that last updated page.
Just gauge your priorities at this point in your comic's life. What's best for your growth, your comic's growth, and your audience growth? Experimenting is vital to the process so I wish you the best in this venture!