Hi Tim - welcome! I think you got a good deal. You can't go wrong for $400... and as you can see from your company here in this forum, you have 3000 colleagues who think very highly of these vintage CBs. I've learned a lot in my two months on this site. I'm glad for you its not seized...that would put quite a damper on your enthusiasm.
We're pleased to have another Michigander. We have a loosely formed SOHC4-Michigan group. Chris Schneider (in G.R.) formed a mailing group this summer and we plan some rides next spring. Let me know if you want me to add you to the mailing list.
-Gary
PS....I'm fond of green bikes myself