You don't really need carbon in a well maintained tank, so you can ignore the instructions to change out the carbon <only exception is if you have used the carbon to take out meds, etc.>
2nd option is to cut a hole in the carbon part & dump out the carbon. Depending on your filter, you may be able to put a mesh bag of carbon in. Now you just made youself a 2 piece filter & be able to change the carbon & the pad independently!
80 gal FW with 30 gal DIY wet/dry/sump.
9 fancy golds, 1 hillstream loaches, 1 rubber-lip pleco (C. thomasi), 3 SAEs, small school of white cloud minnows, planted.