So I was doing some digging on why my trackball performance had started to degrade over the last few months and how I could fix it; I assumed it had gotten pretty grimy under there. After searching for information on the best way to clean it I found several forum threads on numerous sites all of which had pictures either missing, or too small to see any real detail.
I followed the instructions on a thread I had found here and took pictures along the way as a way of "giving back" something. So here they are as well as with more detailed instructions.
The images below are thumbnails which link to images that have been resized to 800x533. If you follow the link you can then click on them again for images that are 3456x2304. I have also watermarked them with the BlackBerry Forums image so no other sites rip them off.
Take a small screwdriver, your thumbnail, or any instrument small enough to pry off the trackball faux chrome plastic cover. Do this gently and carefully, it's lightweight plastic so you don't want to break it.
Look at all of the pocket lint and other nasty bits hanging around the outer edge of your trackball assembly.
Carefully pry up the small metallic retaining clip that sits over, and holds tightly in place, the trackball assembly. Be very careful with this ring, it's very small and you wouldn't want to misplace it. Also, this clip bends pretty easily, make sure you don't pinch it oddly and fold it in half, I don't think it would survive being bent straight again.
Remove the trackball assembly. If you have a magnetic tip screwdriver you can place the tip on the assembly and it will attract the magnetic rollers. The assembly is actually stuck to the screwdriver in this pic.
Carefully set your trackball assembly aside. Note the metal tab appears to be pointing down, this is the side that should be towards the keypad, or lower half of the phone when putting it back in.
Get some alcohol and a Q-tip and some canned air if you've got it. Use the canned air on the phone and then swab the internals with your Q-tip. You should have a small amount of alcohol on the Q-tip, do not soak it. Then hit the internals with the canned air one more time to get rid anything that was dislodged by the swabbing, and dry any residual alcohol. Also swab the trackball assembly itself, and hit it with the air to dry.
Note the grime on the Q-tip and think "What the hell is in my pockets?"
Make sure your internals are dry and just check them out in general. LEDs are laid out as follows: Upper Left = Green, Upper Right = Red, Lower Left = Blue, Lower Right = White. The copper pad in the center is the select pad when you depress the trackball.
Reassemble the trackball. Place the assembly itself in with the two side tabs on the left and right, also you want the bottom of the assembly to have the aforementioned "tab" pointing down. Then place the small metal retaining clip into place with the tabs to the top and bottom. Gently press this into place with your screwdriver tip and you will feel it click.
Place the faux chrome plastic trackball housing over the assembly with the tabs facing left, right, and down. Gently press this into place with your thumbnail. I recommend putting the bottom tab into place first and then pressing. I do not recommend using the screwdriver to push this into place as you may scratch the plastic. You're Done!
I wouldn't do this too often or you may accidentally break the assembly or one of the retaining clips, though it doesn't hurt if your trackball is already broken, or functioning erratically. If you do happen to break something or are too timid to try the above, you can always buy replacement parts at bbrepairshop.com. I haven't used them personally, but they do have the parts.
Anyway, I hope this is helpful and good luck to you.