I'll try to answer your questions one by one:
1. How do I move certain text elements to new subgroups within the labels Group. Basically I want a subgroup of Hydrology, Physical Features and Populated Places. I created the groups but want to know how to move the elements.
You can create a new layer or sublayer in the Layers palette. Then you can drag selected objects to that new (sub)layer. I generally create a layer "Labels" with sublayers for the various kinds of labels.
2. Can I then colour/choose font, etc all at one time?
3. How do I then spline certain river features? I assume I can select the feature I want and then manipulate it to make it splined.
Do you mean cutting it up into smaller sections?
4. Not a text question. How do I automatically produe a Bezier Curve from a road? Again, I want to select it and then automatically curve it slightly.
I don't think this will automatically create a Bezier curve, but it will curve angular lines:
- Select all the objects you want to process this way
- Filter -> Stylize -> Rounded Corners (I have a Dutch version of Illy, so I'm not 100% sure about the English menus)
- Set a radius (I generally accept the default value)
5. Contours: How do I split the line to add the contour label?
You can try Martin's overprint suggestion. I've never got that to work myself though: see here
Alternatively, you can use the scissors tool to cut the contour line on either side of the label and then set it to no stroke (or delete it alltogether).
6. lastly, How do you add a scale bar and North Arrow in Illustrator?
Tricky, unless you're using the MAPublisher plug-in. You may want to do that in Arc because it's quite difficult to get that right in plain Illustrator in most map projections.
Hope this helps.