Upgrading 4.8 -> 6.0

[gandalf]

  Hello Guys,

I would like to upgrade my server from 4.8 to 6.0. I think I know how to 
upgrade a system, I already did that for 4.3->4.8. I need the upgrade 
because some ports starting to throw errors and refuse to build. :-(
It is a production server and I need to be careful. I have some questions:

1. Is it okay to use 6.0 for the production server? (I already have 
another 6.0 and tested it with various apps; it looks good but...)
2. The server is using a special .so file that was compiled for 4.8. We 
do not have the sources. Will this shared lib work with 6.0?
3. Should I upgrade to 5.4 first, or can I upgrade directly from 4.8 to 6.0?
4. Is there any special documentation that I must read before I upgrade 
to 6.0?

Thanks,

   Laszlo