Have you detached the cable from the caliper yet? How about pulling th4e cable out of the casing? Next would be removing the inner cable from the lever, here there's some variation in cable end and the lever's capture design but once the cable if free from that othet stuff the inner can usually be fished out of the lever. Keep track of the casing end caps as they might be specific to the lever. There must be dozens of videos out there as well as a number of repair manuals available on line. The Park Tool Blue Book comes to mind. Andy