Downtube shifter service

[spymaster]

Hi all, is there websites/instructions out there on how to take off and re-install downtube shifters on older road bikes? I have an old Bianchi to which I want to give a new life and the Suntour shifters on it seem a bit stiff. The knob which sets index/friction doesn't want to move either.
The screws on the sides seem to be the obvious place to start but I'd appreciate visual instructions like Alex's great videos so that I'm better prepared and won't catch any surprises. Thanks in advance for your feedback!

[spymaster]

On closer inspection there are no screws on the sides; only a black knob for changing between index/friction (which doesn't budge). Now I really have no idea how to take these shifters off.... Can anyone shed some light? Thanks.

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[spymaster]

Okay I just figured it out. The black knobs ARE the bolts, which I should be able to turn by hand. They were a little too tight to begin with so I used pliers for the initial twist.
Not sure if it's because of age or by design, but I gotta loosen the black knob quite a bit (and subsequently tighten it again) to adjust the grey knob inside between friction and index. This is unlike the Shimano SIS shifters I've seen where it's just a keyed ring you can turn that 'clicks' between SIS and friction without ever needing to loosen the bolt.