I am not really in the business but, i have been involved where i have seen a lot of printing in and out of house.

I would recommend just standard weight paper, it is 80gsm in Australia, not sure is it the same in the US or is it 75gsm i have seen some different things about this i think. There isn't to much difference but the paper weight can affect the look if it is double sided depending on your printing method.

Unfortunately the inhouse printing question is a hard one to say for sure on either way not knowing pricing in the states.

In Australia on high Volume print jobs you can get really low prices Eg. One places offers 6000+ copies for $0.04AUD. Which if you take into consider the costs of owning a printer capable of that that quantity in a reasonable amount of time then it is actually quite a good price since it means all you have do is go to there shop drop it off and it is done.