The VANOS is an actuator on the front of the head, which drives the camshaft. The actuator can be changed easily (relatively - look for the DIY in the E46 section), but the parts connected to the camshaft/chain is harder.
The Valvetronic is integral with the head and valves. The eccentric drive motor is easy, but nothing else is - you have to dissamble the valvetrain.
Neither requires the head to be removed, but it's not easy; unless you're going to DIY it's probably better to buy a head.
What is broken?