when putting a triple on a bike that has bar-end shifters (DA), do you need to change anything besides the crankset? On STI I know you have to also change the shifter but I’m not sure about how it works with bar-ends.
You will almost certainly have to change the BB. Your existing BB will not provide enough clearance between the smallest chainring and the frame.
You will probably want to get a long cage rear derailleur. Otherwise you won’t be able to get to all the gears. I have successfully used a short cage derailleur with a triple, but you have to be careful not to make impossible shifts. The results could be a disaster.
You will also need a big cage front derailleur. You double probably won’t cut it.
I should’ve been more precise in my question: I know about the BB, I probably wouldn’t go long cage at the back (and just be careful with the shifting), I didn’t know about having to have a ‘big cage’ front derailleur, though, thanks. Still wondering about if I’d need to change the bar-end shifter or not 
There is no change in the rear wheel shifting so the rear derailleur and shifter is unchanged. The front derailleur is friction shift, so your bar end shifter will work for both the double and triple.
thanks, for some reason I thought even the front bar-end was indexed (rather than friction). I don’t have the bar-ends yet so I guess that’s where the newbieish question comes from…