The stacks are very easy to install - You'll probably still need the bottom plate of the air cleaner if you're also using the CB Perf. hex bar linkage, but you remove four nuts, pop on the stacks, re-install the washers and nuts and then affix the air cleaner elements to the tops of the stacks (they also sell covers for the stack tops). That's it.
I can't remember how tall mine are. If I get out there later I'll measure them and report back.