You could go non-power, but for a vehicle of this size it will take some pretty hefty leg effort. Some people don't mind that, others find it pretty annoying. It really depends on your own preferences. If most of your driving life has been with power brakes, you probably won't enjoy manual discs.

Here's a link to a site that spells out what your car needs for the conversion. There are some drawbacks, so think how those will affect your driving style. Alternatives would be the aftermarket kits. They will cost a few (and I really mean few once you do all the upgrades to used parts to make them "like new") dollars more, but might offer (depending on who you go with) fewer compromises.

http://www.goatsgarage.com/d2dlft.html

http://www.buickperformance.com/discbrak.htm

And here's a link to an aftermarket supplier of a quality system. http://www.mpbrakes.com/db1741pe.htm