The plunge router base (RA1166) is 9 3/4" fully extended and about 7 3/4" if you lock it in the "depressed" position. These measurements are without the router in the plunge base.
On the second question, I can't really offer any suggestions since I have just got/started using a RA1171 table with the router and use the wrenches that came with my router for bit changing. It's not the most convenient method, but it works and I'm all about keeping tools to a minimum when possible.
As far as getting a plunge router base, I likely wouldn't buy one if I didn't already have one. The kit that included it was cheap enough that I went ahead and got it when I bought my Bosch 1617, but the standard base had a lot more adjustment to it than I initially thought and therefore the plunge base isn't really necessary. I will say this, if you get the plunge router base, consider getting the RA1054.
I bought the router attachment for my Dremel and it came with a guide like this and it's VERY useful for freehand routing with bits that don't have a guide wheel.
The only reason I haven't bought the guide is because I intend on using my router primarily with the table and very little freehand use, so it'd be another tool laying around and in the way. I'll buy it when I need it.
Hope that helps....