- Check with your local Apple store, they do charge labor, but the parts are cheaper than here.
- On your model, the glossy screen holds the airport card under the clutch barrel. But the anti-glare does not. If you got the anti-glare from the factory, there is an additional bracket that sits on top of the optical drive, where the airport card is held. You would need that bracket, and an additional cable to connect the airport card.
- It's most likely your battery. Try taking out the battery, and using your computer plugged in. You say that you're using a 3rd party battery, it may be just slightly off in design, and pushing up on your trackpad. Another possibility is that your bottom case is slightly bent. If the center is slightly higher than the sides (frowning) it will cause this. You may need to do some 'manual adjusting' (bend it back into place). Do this with the battery out.
- If by 'looser' you mean that it is easier to open and close, there is no way to fix this, unless you replace the hinges. But loosening the six screws does not affect this at all. (Also, it may just be paranoia, you'd be surprised how we can think things are different after we take them apart) If it is not fully connected to the main body anymore, and moving around, then yes, you just need to tighten the six screws. Best thing is to make sure that everything is lined up, then tighten until it won't anymore, don't go so tight that you strip the screws, but fully hand tight. The easiest way to line it up is to have the display closed, loosen those screws, then use your fingers to make sure both sides of the top case and display housing are flush, as well as the front.
- If it is wiggling back and forth in a direction perpendicular to the display (forward and backward with the display open), then you may be able to fix it by tightening some hidden screws. Sadly, there appears to be no pictures in the guide here, and I don't have that model to show you myself. Once you remove the display assembly, you just need to remove the clutch barrel (the black plastic piece covering the center bottom portion of the display. It slides to the right with some moderate force, then pulls off (pulling perpendicular to the display). If you look at the display from the bottom, you should see two screws on each hinge holding them in place, you just need to tighten the ones that are loose. You may want to temporarily reattach the display to the body while the clutch barrel is still off, just to make sure everything is lined up properly before tightening the screws. Then just put back the clutch barrel, carefully routing the cables back through and sliding it back into place.
- If you are near an Apple Store, go in and ask them to replace the back cover only. It only costs $29 +tax. Much cheaper then doing it yourself