Those are very good questions Phillip.
From everything I have gathered, the principal benefits of the legislation are economic to commercial outfitters and local businesses, as well as protection of the area from oil/gas/mineral development, and yes, Browns Canyon is currently the most commercially rafted stretch of river in North America.
The same agencies will be in charge of management as now. The jurisdictions are separated into Forest Service in the higher elevation regions, BLM down lower, and the Arkansas Headwaters Recreation Area along the river corridor. I do not believe there are plans to add any additional personal for this purpose.
I can't speak for which part of the Antiquities Act they are principally relying on for the designation status, and I don't think there are really any major academic organizations involved in the proposal. The biggest player from a conservation standpoint locally is probably Garna (Greater Arkansas River Nature Association), and nationally the Sierra Club. I have done pretty extensive exploring in the region and I am not aware of any cultural sites. It's not unheard of to find an arrowhead, but I have not seen or heard anything of ancient dwellings, potsherds, or prehistoric art.
Doesn't really seem like there is any one good spot to gather information on this proposal.
Here is a link to the bill itself:
Sen. Mark Udall's Bill to Create the Browns Canyon National Monument
and here is a link to all of the AHRA's publications, including the complete Management Plan as it stands now:
Arkansas Headwaters Publications | Colorado Parks and Wildlife