Well, some places over the net install them for free, if U send your slide to them, and buy the sights from them. But, then ya usually have to pay shipping both ways. Its not too bad on only the slide, though. But, I prefer to just buy the sights and have a local guy put it on. That's typically $20 in my area.
I like that because if they end up being slightly off, U can go back later and they would adjust it for free (since they are the ones who put them on).
As for which brand - some people like trijicon. Some people like meprolight. I personally like meprolight. They are usually a little bit cheaper too. Is there a shop near U that carries both, so U can look at each and see whick U like better?