It's a wagon, right? If so, you need to remove the entire carpeting from the right side of the trunk. That will also take care of the grill in front of the sub. Once you get that out of the way you'll see that taking the sub out is just a matter of undoing 3 screws and unplugging one connector and that's it.
good luck finding the right size replacement sub, its hard to find a good quality sub that small. i tried, i ultimately gave up after finding the right size one, having it sound like garbage, and brought it back to the store i got it. so i got a 12" with a box and put it in the back... btw saab will charge an obsurd price for the replacement factory sub. around $300 or so... so like i was saying. good luck. :cheesy: