Tamron 28-300mm AF dead - repair or leave?

I have a Tamron 28-300mm VC f/3.5-6.3 (model A20), a bit over two years old. Not the most amazing lens in the world, but, I've managed some shots I'm pleased with, nonetheless.

A few months ago, the stabilisation began behaving erratically, sometimes locking in one orientation, not freeing up until the lens was remounted. Not a big matter, as it wasn't something I used very often, so I wound up just turning that off.

However, a few weeks later, the autofocus sometimes didn't engage. Within a week or two, it had completely ceased functioning, effectively becoming manual focus only. The D90 is fine, as my Nikkor 300mm f/4 works as beautifully as ever in AF mode. The contacts on both the lens and body have been cleaned, to no effect.

My question, then: is it at all feasible to repair a lens like the Tamron at home? It's doubtful it'd be worth having it looked at professionally, as a used replacement probably wouldn't be much more expensive - given the optics, they can be found relatively cheaply. Might it be something simple, like a fragile broken wire? (Obviously, it's impossible for anyone to diagnose something like this remotely - but, maybe there are known failure modes for this lens)

(I'm pondering a cheap replacement, for now - the Nikkor 18-70mm f/3.5-4.5 sounds like a good candidate. No VR, but sharpness sounds good for the price, and I'd certainly appreciate the extra scope at the wide end)