Suggest you check out the Cheoy Lee Owners Association website:
Lots of good stuff there, including restoration.
I've owned a Cheoy Lee-built boat for the past 17 years, have visited the factory site a few times, and have followed Cheoy Lee's boats since I saw the first one in 1965...a Rhodes Reliant 41.
As I recall, the Offshore 31 sailed fairly well, but was certainly no speed demon.
I'd say that restoration is a BIG project, no matter what. The hulls are very well built, hand-laid up with very few if any blister problems. The teak work, while beautiful, can be a bear if previous owners haven't paid attention.
Whether or not to willfully engage in such a project should be predicated on your intentions. If you want a project, have lots of time and bucks, and just want to make the boat beautiful again it could be fine. If you're talking about making it into, e.g., a modern cruising boat with the bells and whistles, new rigging, sails, etc., it could be a VERY expensive project.