You should. I believe all of New Testament is still on Baka-Tsuki, but you'll have to look elsewhere for the original 20-something volumes after Yen Press licensed them and Baka-Tsuki took them down. I believe there are some sites that do host the original series post-translation, but I can't nail them down for the life of me.

I did manage to read through them right before they were taken down, though. Document of Constantine Arc is cool and all, but OH BOY BATTLE ROYALE ARC.

That aside, I think the best thing about it all was the final arc. If you get a chance to read it, DO SO.