Here are a couple of guides for removing the lower and upper glove box, just pictures. I didn't produce the pictures, I simply collated them into a pdf after finding the information elsewhere. I used them to remove the lower and then upper glove box to remove the ECU on a 1996 LS400, the guides were accurate for my car and I didn't have an issue taking them out. Putting the lower one back wasn't as easy as taking it out but I got there in the end with a bit of patience...........
Update: Just one tip for re installing the lower glove box. There is a lower section that can be un-clipped and then installed after the rest of the glove box is installed again, I recommend doing this as it makes it a hell of a lot easier.