Upgrading Clients to 14 using SCCM or autoupgrade

Greetings,

Ive been looking through articles about the possibility of using SCCM to upgrade our clients (1000+) to v14 or using AutoUpgrade. Other than the firewall ports needing opened between SEPM and the clients, i had a few additional questions:

1. Can the GUPs at each location be used as a distro point for client upgrades or are they just used to proxy definitions?
2. Can I leverage my LU policies to point clients to the internet (symantec liveupdate site) to download the client upgrade or can it only come from the SEPM via package build?
3. From what i have read, do I need to build a separate package for each AD OU i have imported or will the single package with the single sylink.xml file pointing back to the SEPM be enough? what happens if you have multiple SEPMs for redundancy?
4. Depending on Question 3, If i only need one package built and only one sylink.xml file used, can this be deployed via SCCM reliably?
   1. Does the existing client need uninstalled via SCCM or can the package be built via SEPM then imported into SCCM for deployment and it will upgrade the clients correctly?

Thanks so much for the assistance!

D.J.