Thank you all so much, for all this amazing information. As a 3.5 Nepophyte I have really enjoyed reading it all
Thanks also for the Pathfinder recommendation; I have both the PDF and physical copies of the 3.5 2012 updated core books, so I'll be starting out with 3.5 and see how it goes.

Now I'd like to start with a prepared campaign.
And perhaps some of you have some great pointers on this as well.

I was considering starting with Sunless Citadel (I know it's a 3.0 but I guess it can be converted pretty easily?), but other alternatives are Age of Worms from Dungeon, or perhaps even Paizo's Rise of the Rune Lords (the 3.5 original version).
Can you guys recommend one these options? Or some other?