Ken,
It is ideal if the carb can stay inside the cowl, however I have ran mine outside and it works very well. To answer your question, a servo can operate the choke, but it would save you some weight if you can simply hook a rod to it and do it manually. You can leave a hole big enough to get a rod with a hook on the end in the cowl and dress up the hole with a rubber grommet. This can sometimes be a bit of a pain, but it is the way I prefer to do it to save weight.
Good Luck,

Jeff