loose spoke that will not screw back in Noticed that my rear wheel is pretty un-true and is hitting the brake pad / wont spin freely. 

Decided that I would try to fix it myself before opting to pay 20 bucks. 

There is one spoke that is completely loose. The problem is that one i turn the spoke it does not tighten, nor does it feel like its being screwed into anything. 
(my spoke is straight all the way - i have this wheel) 

Questions:
1. Can I fix this, or do I need a new spoke / bike mechanic
2. Does riding like this make things worse (aside for greater wear on my brake pads)
The spoke and nipple are turning together? This wheel uses straight spokes. Don't think it's likely, but the notch could be stripped at the hub, meaning there wouldn't be anything you could do about it besides get a new hub.

I think more likely your spoke nipple is probably stripped. Try to get another one from somewhere that is the same size as the ones already in your wheel, and try to replace the bad one. You just need to take off your tire and rim tape, and pull the bad nipple all the way out. Then get another nipple (2.0mm diameter) and thread on. See if it works. Could also be bad threads on your spoke.