A couple of years ago I had both done.
It was a new type of agony that words cannot begin to describe.
The actual piercing wasn't that bad (though still quite painful), but the first couple of nights I couldn't sleep properly. The sheets rubbing on them is really painful / annoying and you have to sleep on your back.
My suggestion: do it in summer.
After a while it wasn't so bad. You gotta really look after them for a while until they heal up. The place you get pierced will tell you everything you need to know (or at least they should).
Once it's done, you need to wash yourself with anti-bacterial soap (easy to obtain from a chemist), and use saline solution to wipe it / them down (again, available from most chemists).
At the time I was working in fast food and had to wear an apron. Unfortunately the straps rubbed right on the piercings so they never healed properly and I took them out after about a year. (I did it myself with a pair of pliers - not recommended!)
Although it hurts a lot more, I advise getting both done rather than just one. With one it just looks like you wanted to do both but chickened out after the first one.
Right after I had them done (a few minutes) I got a really euphoric high and was giggly for about three hours.
I suggest band-aids over them for the first few weeks to stop your shirt from rubbing on them. It / They will be really sensitive for a few weeks.
Also, if the place doesn't explain it to you, make sure nobody goes licking it / them until they are healed. If you get foreign saliva in your bloodstream you could get septicemia (blood poisoning) which is never fun...
