your favorite gear doesn't work no more, cause that's the gear you spend most of your time in.
wears down faster than the others as the chain stretches. you replaced the chain which meshes
with the other cogs, but your favorite is too worn. ooops.
the sun race cassettes work with shimano systems.
https://www.ebay.com/itm/393407373836
buy yourself a cassette tool at the same time, something like this:
https://www.ebay.com/itm/403638707857
chain whip? you don't need no stinkin' chain whip!
you got a chain you just removed.......use that.
with the wheel removed, wrap once around one cog, wrap the other end around something.......i use the porch railing.
that'll hold the cassette while you remove the lockring with the tool and a big ol' crescent wrench.
for repairs on the road, i found (after much searching) a 6" crescent that would open enough to fit the casette tool.
and when i install a new cassette, i tighten with the tool by hand, then 6 clicks with the crescent wrench.
with that tightness, don't need a chain whip to remove on tour. i can hold the cassette.....with good padding....
in my hand to pop the lockring.