How many pools, replics, master VMs are you dealing with in your environment?  I normally recommend a "swing" migration whereby you leave your current Ifrastructure alone and build a new infrastructure.  The nice thing about this is that all your users will have to do is log off and back on and now they will be on View 5.  The negative is that it takes more hardware resources, but normally its doable.

I would definately go to View 5.  There are countless bug fixes in this version plus some very nice new features like Persona management.

Also, I would encourage you to call in a thrid party as you "have limited vm experience".  I know when I'm onsite I spend 75% of my time educating, the actual upgrade isn't that difficult.  Making sure the client understands View and feels comfortable when I leave is the most important thing.  Just food for though, I'm not pushing my wares or anything. 

Gunnar