rickyp - yep, you're right - there are a whole bunch of sight makers for 1911s and no, the dovetails are not all the same.
You will need a rear sight with a dovetail that "replaces standard 1911A1 rear sights", on slides that have not been modified to take sights with larger dovetail bases.
Check one of our sponsors, Mid-South Supply for their offerings of rear sights and also check Brownells to see what they have. A set of used sights or a used rear sight is usually a gunshop or gun show item.
Style - up to you and depending on how serious a paper slayer and bunny popper you are. I get a pretty clear sight picture with a fixed rear Nowak style sight and blade front. You can get fully adjustable sights if you wish.
Rear sight adjustment tool??? Do you mean a hammer and a drift punch?
Most non-adjustable rear sights simply drift into position and you adjust them for windage with a hammer and punch.
Some adjustable sights may require fitting but the base part of the sight will drift into position in the same manner as the non-adjustables and then you make minor corrections with the adjustment capability of the sight.
And Lynnie and SharonAnne can jump in here anytime. HTH. Mikey.