other than the stock on the other side, is there anything special about left handed sets? possible buyer is left handed.
Chanter keys, particularly the Fnat might be more difficult to reach by a leftie playing a rightie chanter.
Blowpipe on the other side too (or things could get ‘weird’)?
Chanter keys are the main issue - not a problem for the c nat but for the others it could be.
You’d need a new bag - obviously - and possibly a new stock.
Don’t forget to invert the clack valves in the bellows and blowpipe.
Jon
thats what i thought, pretty easy to switch. thanks gents
I’m playing a “lefty” set pieced together from various right-handed components and a new bag. It’s a pretty managable solution for getting started with used equipment but I look forward to the day I have my own left-handed chanter (and eventually set). Depending on the chanter make you can also have issues with ergonomic hole drilling (i.e. back D placement) or ergonomic scalloping - those are the two things I’d watch out for most when selecting a chanter other than the keyblocks that were already mentioned.
I got started with a Preshaw chanter that had both of the above ergonomic frustrations and I had a heck of a time keeping my hands relaxed and the holes covered (when looking down the stick, holes up, I could see a slight right-handed bias in the scallop and the back D was offset as well). When I switched to a Kirk Lynch chanter with no scallop it was a night and day difference.
For the chanter, everything important has been said.
On some bellows, the arm and waist straps of the bellows are fixed in an oblique position, if so, the position will have to be reversed.
The main stock will need some reworking, although not necessarily replacement, also the loop in the bass drone needs to be reversed. On a full set, the regulator key pins will need to be reversed, or else they will come loose and fall out (I know what I’m talking about…), and obviously, the bass reg separator has to go to a new position. I would strongly recommend to get this work done by a pipemaker, it’s not a DIY job.
Everybody’s different so I don’t know in your friend’s case, but I’m left handed and play a standard set of pipes (I play a regular right-handed guitar as well). The way I think about it, the two hands are doing different things but both (to me) require equal control and dexterity. The disadvantage of a left-handed set would be that it would be hard for another piper to use the instrument (in a lesson setting, for example). Just my two cents. 
Right, a left handed person doesn’t necessarily have to play a left-handed set; especially if they are new to playing this or any instrument. I am actually right handed and began playing whistle with left-handed posture because I didn’t know any better and just did what felt natural. I tried switching to right posture for the pipes but the linear connection between my two hands was already too deeply set and it wasn’t connecting for me.