I changed the oil in my 1st gen (gray) supercharger on the 4runner awhile back and it can be done but is a pain. Buy two bottles of supercharger oil from your local Chevy/GM dealer (way cheaper than Toyota) get a cheap pump from say HarborFrieght and pump out what ever you can, make sure and measure what you take out and put that back in. I noticed on mine that it is basically like a differential in there with nothing but 3 gears spining so in my opinion if you put a little more than recomended it should be fine. If you can only get some out, add the new drive it a bit and then repeat to get some of the old out again.