| | How about just get a new trackball?
I have taken mine apart to clean it with the intention of getting the trackball white/clear again...after following the instructions and carefully removing the trackball assembly and cleaning all the surfaces with 99% isopropyl alcohol (with the power off and the battery out), I found that the trackball works better now (more responsive), but it didn't come clean like new again...looks like the reason behind this is because the trackball is porous, i.e. it soaks in oil and dirt from our fingers.
I have found replacements on ebay for dirt cheap (and the seller has a 100% feedback score!)...I'm looking at $6 plus shipping ($6 again, so $12 in total!). Most online stores are selling this little assembly for around $50!
There is also a replacement lens cover so if yours is all scratched up like mine, a lens cover replacement is the way to go...it is about $10 on ebay with shipping!
There are also replacements for everything else you can think of, the battery, the battery cover, the faceplate, the keyboard, you could theoretically replace everything replaceable for around $60!