The plastic fasteners you talk about should have a little circle in the middle, if they do, push them "in" to the rest of the clip until they click, then pull them out. Once the trim panel is off, there will be a couple t-25 torx head screws goind up on the ft end of the fuse panel. Once those are out, you will be able to lower the front of the fuse panel and the rest will pivot of the back fixing point. You do not have to remove the negative cable from the battery, but it is always a recommended step when dealing with electrical items. The fuse/relay panel may have a zip-tie holding the wiring loom to the dash frame, as there was a campaign we did to isolate the wiring to fix a fire hazard, so make sure if you snip the zip-tie, to reattatch the harness with another.