IIRC, the older lewmars used a circlip to hold the top on, rather than having a threaded piece like the newer ST40s. This document should help you disassemble them.
IF you're really worried about the butyl tape getting in, tape off the openings and then bed them. In reality, you're bedding the base of the winch first...and then reassembling it...so you should be able to easily clean off any butyl tape that does ooze up into the winch proper before it can get to the gears. All the parts drop down from above IIRC.
The black plastic tab actually is meant to go into a slot on the back of the chrome line stripper. You probably disassembled the winch too quickly and didn't notice that minor detail. The stripper arm should basically point to where the person tailing the winch is going to be so that the sheet ends up falling into the cockpit by them as opposed to falling off someplace else.
IF you're really worried about the butyl tape getting in, tape off the openings and then bed them. In reality, you're bedding the base of the winch first...and then reassembling it...so you should be able to easily clean off any butyl tape that does ooze up into the winch proper before it can get to the gears. All the parts drop down from above IIRC.
The black plastic tab actually is meant to go into a slot on the back of the chrome line stripper. You probably disassembled the winch too quickly and didn't notice that minor detail. The stripper arm should basically point to where the person tailing the winch is going to be so that the sheet ends up falling into the cockpit by them as opposed to falling off someplace else.