Moi,
Take a look at iPod integration kit installation guide. That contains step by step instructions on what panels to remove, how to handle passenger side knee air bag and how to remove glove box. I did that when i installed iPod adapter kit (had to drill a hole for iPod cable to the glove box).
You should be able to get the PDF at least from
http://www.sewellpartsonline.com/import/pdf/iPod_LexB.pdf
In general, these accessory installation guides like the iPod kit guide contain a lot of info on how to disassemble/assemble your is250. I've found them very useful and they are available for free (haven't found too many shop manuals for free).
Very helpful advice, thank you! Is the nylon pry tool or the nylon trim removal tool anything special? If so, where can I get one?