I have a 68 Dart 340 with manual steering and brakes, the only two issues I have with the car. I can by a power brake booster from autozone for this car, but can I just bolt that on? And what in the world can I do about the sloppy steering? Thanks for your help I'm still pretty ignorant about this stuff, but I'm learning.

The sloppy steering has nothing to do with it being a manual box. The tierod ends, a-frame bushings, ball joints, all could need replacing. The steering box probably hasn't been adjusted properly in the car's lifetime. Get a service manual for this car. Follow the instructions for adjusting the steering box exactly...and see if there is an improvement. Even if you need a new (rebuilt) box it can probably be bought at your local auto parts store for less than $200.
As for the brakes, you'll probably have to replace the master cylinder and maybe the pedal assembly as well as adding the booster to the system. You'll have to research that.

PHR has the right idea. Late sixties Mopars were famous for bad (rubber) idler arm bushings. Moog used to make a hi performance greasable idler arm assy. for this application. To check slop on the old one, jack up one front tire and wiggle it vigorously. If the idler arm bushing is bad, it will flop up and down big time. Bad Idler arms will cause your toe-in to go away resulting in extreme inner tire wear.