The way I've set up redundant syslog servers is by using a load balancer and shared file storage. I basically have all of my endpoints and my syslog servers log to /mnt/logs which is a shared SAN storage. Both servers have that mounted and can write to it so no matter which server is up, the logs will always be in the same place. I have some additional details in my previous post which can be found here.
Sorry, I only answered part of your question in my initial post. As far as sending all logs to the central location, I just modified the rsyslog.conf and added this line.
In my example, I just want the auth and authpriv logs, you can do . if you want everything. I'd recommend keeping the local logging as well just in case. No reason to modify everything else when the system is made to keep logs for ~1 week depending on how it's configured. As far as Windows goes, I use nxlog as an agent and send all logs via it. You can also use Snare as it's a little simpler to setup if you are not used to nxlog.