I did my taillights last night, and it does look like pulling the assembly is the easiest (maybe the only) way to change the plate bulbs. It's not really very difficult. I would recommend changing all the bulbs while you're at it, though.
Use a 10mm nut driver, or socket. There are 7 nuts that hold it on (at least that's how mine is). Two each are on the edges of the lid, and three are across the lid under the trim. It'll be easier if you have the tool to pop those (6) panel fasteners that hold the trunk trim, but you can also get them with a flat blade screwdriver.