1) Culmann Magic 2 for lightweight (folds flat anto my bag). Bogen Manfrotto 3021S ($75) for heavier more stable support. For full height I purchased a 3001 bogen for $35 at a camera swap.
Note: I wouldn't recommend the magic 2 for anything but a light camera
2) Monopod is also the center column (3259) that fits either the 3001 or 3021. Sadely, they don't make the center column/Monopod unit that fits the new models. This is the reason why I specifically went out of my way to purchase the older Bogen models.
3) Depending on what you shoot... most likely yes.. it is worth it. Almost everyone here will agree that Bogen/Manfrotto is a great way to go. IMO, don't be afraid to purchase used as there's not much to a Bogen/Manfrotto tripod to break.
For cheaper options (more compact too), I liked velbon's offerings.
Search.. there's more info in past posts.