STOP.
1. If you try to rip a damaged/mushroomed lifter out the top of the lifter bore, you'll likely damage the lifter bore, which means the engine gets torn-down and--at minimum--the lifter bore is bored and sleeved with a bronze bushing. This will be VERY EXPENSIVE.
2. They sell tools to remove VARNISHED (NOT MUSHROOMED/DAMAGED) lifters from the top of the bore. The varnish is relatively soft, gets scraped-off the lifter as the lifter is forced-up through the cast iron lifter bore. The folks selling the tools will not pay for the damage they cause if you misuse them on damaged lifters where the steel has formed burrs that will gouge and score the iron bore. See #1.
3. If the lifter is relatively new, (9000 miles) and can't be pulled out of the bore easily, the bottom has mushroomed, because varnish doesn't build-up that fast. See #1. The camshaft is ALSO ruined, and will have to come out.
4. Any lifter that will come out of the bore like normal, comes out. Any lifter that won't come out of the bore, gets pulled upward to the limit of it's travel, without forcing it. Slide the cam out. Push the lifters DOWN to remove them after the cam is gone. You'll need a cardboard or thin sheetmetal half-circle "tray" slid down the cam tunnel to catch the lifter(s) as they come out the bottom of the lifter bore, or else they'll fall into the oil pan.
5. IF (big IF) there is a miracle this Christmas season, and that camshaft is not totaled--and I don't think this is at all likely--you could poke it back into the block, replace the other lifters in the same lifter bore they came out of, drop some other Chevy lifter on the lobe that had the damaged lifter, run the break-in procedure again, and IF (big IF) that lifter is the same functional height as the one you removed, you'd be fine. MAYBE the "new" lifter is taller or shorter than the one removed, which MIGHT mean you need a shorter or longer pushrod on that lifter. I hate to even mention this, as it's so unlikely that the cam will be reusable.
6. So the easiest option if you insist on replacing one lifter is to buy one lifter of the same sort you bought to begin with. I think that would be a waste of time, money, effort, and enthusiasm, 'cause you'll be replacing it--and the cam, the rest of the lifters, and the bearings, maybe the pistons, honing the cylinders, etc. when that cam lobe goes entirely round and fills the oiling system with metal debris soon thereafter.
7. LIFTERS ARE ASSEMBLED AT THE FACTORY WITH A "SELECT FIT". The lifter body ID is measured with ultra-precision equipment to the zillionth of an inch. The lifter plungers are measured to the zillionth of an inch. Then they're sorted into size-specific groups, so the bodies with the biggest diameter get the plungers with the biggest diameter, the bodies with the smallest diameter get the plungers with the smallest diameter, etc. Hydraulic lifter clearances are MICROSCOPIC. Hydraulic lifters are the highest-precision parts in an engine, by far. You WILL NOT mix parts from one lifter into another lifter.
8. NOW you know why it's nucking futs to assemble an engine with a flat-tappet cam in this day and age, ESPECIALLY if you have a block that's already set up for OEM roller-lifters.