DSM6.1 and Plex Server upgrade version

Hi
I have a DS1513+ (Intel model) DSM 6.0.2-8451 Update 8 and am I being prompted that DSM 6.1.2-15132 is available. I am also being told in my plex server that PlexMediaServer-1.7.5.4035 is available.

My question is
1. Are the two version compatible?
2. What is the steps to upgrade?

I have read various threads about people upgrading and plex not working.

Thanks
Andrew