I have a PSA Freedom upper coming, and am not sure what the best sight would be height-wise for the rear, and even if there is one on the front.  I am pretty green to this, and can't find what I need to order the right thing.  Any help is appreciated.  This is what is coming:

http://palmettostatearmory.com/index.php/ar-15-05/barreled-upper-assemblies/psa-16-mid-length-stainless-1-7-freedom-upper-without-bcg-ch.html

Is there usually a post installed on the front sight, or do they leave that up to you?

Post is installed already.

All you'll need is a rear sight. Just about all of them (aside from micro sights) are the same height. Just pick which one you like the most.

Thanks a bunch for your help!