Check the ATF level in the gearbox with the engine running in park (Green handle) Jerky shifts usually indicates low fluid levels. The colour of the fluid should be cherry red, if it's brown this indicates old oil/ burnt friction material from the clutch packs. You can get a filter and gasket from vw heritage for the auto box. You have to remove the pan off the box as there is no drain plug.
Don't flush the fluid, just drain and refill with new fluid.
Pretty much everything for these engines is easy to find online, I wouldn't recommend one particular supplier of any one thing, best to research yourself in my opinion. If you're looking to buy valve guides then you'll be removing the head and having it machined at a shop, get them to source bearings, rings, guides etc.
I bought guides from GSF I believe and had them pressed in when i decked the head, the ID is usually undersized for the valve stems so they have to be reamed anyhow, much better the machine shop does this that DIY.
But yeah, you can buy pretty much everything on the typical sites, depends how much you want to spend really. But if it's just looks then degrease it and paint it. No point rebuilding a working engine.