Wireless Lan Controller Questions (Extreme Networks)

I'm tasked with searching for a Wireless LAN Controller for my company. My only rule was that it has to support about 50-100 access points. I'm pretty sure I've narrowed it down to the Extreme Networks C35 Physical Appliance.

I have a history with Cisco and a perfect "Cisco World" environment. I recently learned about WLCs but only when it comes to Cisco, and obviously not enough.

Here are some questions I have regarding WLCs:

1. Do WLCs only work with specific enterprise access points? For example would the C35 WLC be able to manage Extreme Networks 7632 Access Points AND Motorola access points? Or would I be looking at replacing some access points to make them all the same?
2. In your experience how hard is it to implement a WLC into an environment that's already setup?
3. Are multiple WLCs needed at every building if the access points are on the same network or would they still be able to contact the single WLC? ( I'm pretty sure I know the answer to this one but it doesn't hurt to verify)
4. What advice or tips would you give regarding this kind of task?

Thank you in advance for any questions answered or input, it's greatly appreciated.