If the 2.0 you're talking about is an ABA, then it's a pretty common conversion (as far as watercooled VW engine swaps go). I think, though, that all of the New Beetles use a different 2.0 (code AEG or something like that, I think).
If it's an ABA, you're home free - use an A2 dual outlet exhaust manifold with an A3 dual inlet downpipe (or you can buy a downpipe from Techtonics - they sell lots of parts to help make this engine swap easier) for the exhaust. You can buy a block-off plate kit (for the breather holes in the crankcase of the ABA) and the correct head gasket from Techtonics. You will need both ignition distributors to make a custom one. The easiest way is to buy the distributor adapter ring from Techtonics, remove the drive gear from the 1.8 distributor, install the drive gear from the 2.0 distributor, then use that (along with the adapter ring) in the ABA block. The alternative is to disassemble the 2.0 distributor and replace the windowed-wheel (for the hall sender) with the wheel from the 1.8 distributor - then put it back together and you can use that distributor without having to buy the adapter ring. When you're all done, the throttle body will rub against the rain tray a little (especially when the engine rocks under acceleration). How you deal with that is up to you - most people just bend the rain tray out of the way a little bit.
If the 2.0 engine you're talking about is not an ABA... then I honestly have no idea how feasible it is.