All the errata was collected in one PDF at one point. I don't know that I can share it, but the PDF I have is 139 pages and titled "UpdateCompiled.pdf" It is organized by book, and page, so its easy enough to check any specific game element for an errata. There is also a 4e database at this link which appears to be complete and up-to-date.No, but I kind of wish I was. I've heard a lot of praise for it since it went out of print. The problem is, I wouldn't even know where to start if I wanted to because it underwent so many rewrites during its time in print. There were, IIRC, 44 pages of errata at one point, skill challenges alone underwent many revisions, the monster maths were heavily revised at one point, and the Essentials books were er... essentially... replacements for large chunks of the core books. If I wanted to start playing today, what books would I need to pick up?
I'd also note that the errata, while they did make a bunch of it, is not that big a deal. You can ignore it, nothing is grotesquely broken or unworkable as-written. DMG2 and the Essentials RC have complete SC rules that work fine (the original ones actually work fine for many people too). Basically the Essentials RC is a perfectly good rules reference for all the 'core rules' and incorporates updates and changes made over the life of the game.
All 4e material works fine together also. There really are no incompatible versions of things like happened with 3.0 and 3.5, everything works with everything else. Anyway, you can use the Essentials material, and/or just the original 3 core books, there's plenty there. A lot of the books are still available easily on Amazon in print, and I guess WotC has released PDFs of at least some for sale. dndclassics.com 4e page lots here
I'm sure you can get books for cheap on other sources too, despite all the FUD 4e sold quite well and had large print runs. There's a ton of books out there.