Digital signage is a reasonably seasoned and robust industry these days.
Call in a few vendors and I’m sure you can get bids galore.
If you have the time – the industry expo – DSE – starts in 2 weeks – Feb 23rd in Vegas.
One area that people new to the subject tend to overlook is display hardware life cycle and how frequently you’ll need to replace expensive components, like your screens. A “mostly on” cycle on big screens can age them up pretty quickly with static element “burn in” and other factors important to their useful life cycle. Some technologies like Plasma display have BEAUTIFUL pictures – but may burn in more quickly than LCD displays.
So ask alot about costs over the ENTIRE expected useful life of any system you consider.
Oh, and be careful about companies who subsidize the hardware with long-term hard-to break service or content management contracts. Be clear about who will update the content – on-site, remote, or a combination – and what that’s going to cost over the life of the system.
Good luck.