Try it out here in Ireland first, then decide whether you want to go on the Canal du Midi. There are canal boats for hire here, there's a company a couple of miles east of Tullamore (Celtic canal cruisers?) that hires out nice looking narrow boats so you could try a weekend and see if you like the amount of work involved in going up and down through locks.
The Canal du Midi is a lot bigger though, and you might want to go on the Shannon to get an idea of the scale of the waterway. Emerald Star is one of the big outfits (belongs to First Choice in the UK AFAIK), they have lots of modern boats. There is aother small outfit called Tara, based in Carick on Shannon and they are reputed to be cheaper. More importantly, their boats are good steel hulled cruisers, not the Tupperware that is favoured by the big companies, so if you have fears of getting holed and sinking without trace, stick to the steel hulls! Because of the method of construction, these types of boats are much more roomy and less claustrophobic. I know, I have owned a steel hulled boat for many years and I would never go back to sailing in a lunchbox.
A few days on the Shannon is a great way to unwind, and you get a whole new perspective on Ireland when you see it from the river. Go for it, lots of incompetent idiots do it every week and live to tell the tale (I tend to take evasive action when I see a big green plastic machine steaming at me at full throttle).