I've flown with a lot of first officers, and captains before i upgraded and other people who also have that same predicament, so far into it, just want to wait until the upgrade or some other milestone and start from that point on, but i would still recommend doing it now!
I started an electronic logbook before I went to the airlines which made it much easier, and yes its very tedious to get all the previous hours in (i went back and did all 800 hours I already had before i started my electronic logbook) but it will probably be a lot nicer/easier if you have everything in your electronic logbook, if not the totals and everything else will really never match up....of course you could create one big generic entry, but when it comes to finding out how many hours you have in CRJ-200 vs the 900 at night, it would be pretty hard to figure out unless it was all in the electronic logbook piece by piece!
Don't forget there are electronic logbook services online that you can send in a photocopy of your logbook pages and they will literally create each entry for you one by one including comments and email you back the file to import your logbook