If getting into modification, refurbishment and servicing the 6309 is the ideal starting point with many parts available and doner movements for spares.
With a good quality screwdriver, tweezers and basic tool inventory all you need is patience, good eyesight and the knowledge from the 'how too's'.
And with a little practice you will wonder why you did not try sooner. Being unafraid of getting stuck in (knowing your limitations is important though) opens up a whole new dimension to watch collecting.
Mike