Technically, the recent Nominal Engine Performance improvements you've experienced might be compared with something akin to a 50 Year Old Life-Long Smoker taking up Jogging and after finding he has lost a legitimate (10) pounds from his recent, fresh weekly exertions...
imagines that he has cured himself of all prior ills.
The formerly Badly Clogged Up Screen on the Oil Pump Pick Up Tube might be showing signs of improvement... but the events leading up to that Rash of "Low Oil Pressure" Alert Dash Lights you encountered was an indicator that if there is any damage lurking inside that LL8 Engine Block... it has long since happened and that a few Very Bad Things may still be lurking in the background waiting to raise their Ugly Heads.
As for the Timing Chain R&R, the Biggest Issues with High Mileage, Semi-Clogged Engines are the 'Big Three Codes' popping up; either all or singly as follows:
P0017
P0014
P1345
All of which will focus the Owner's attention on problems involving
Crankshaft and Camshaft Correlation.
Poor Oiling of the Hydraulically Fed Tension Plunger inside of the Timing Chain Tensioner along with the out-and-out wearing down of the Two Timing Chain Plastic-Nylon Guides along with inevitable Chain Wear and Stretch will invite the Crankshaft to Camshaft Correlation (Ignition Timing) Nightmare.
These events WILL require following the well documented actions of performing the R&R of the Crankcase-Oil-Pan, the Front Timing Cover and the Valve Cover to do this entire Cloyes Timing Chain Set R&R.
Performing this work "in-situ" is worse than just Pulling the Motor and doing
ALL of what is required after the LL8 becomes completely accessible once Mounted on an Engine Stand.
@Mooseman has often recommended obtaining a Well-Tempered, Low Mileage GM 4.2L Motor and then conducting an Engine Swap in lieu of doing the "In House" Timing Chain Repair as a
MUCH Better Course of Action to Follow. I concur with this approach.
The Smart Man in this scenario... First Mounts the "Swap Motor" on an Engine Stand and performs the Cloyes Timing Chain Set R&R and De-Mung and De-Carbon Efforts to Clean the Bottom End of any Black Carbon Build Up from the innards (Oil Pick Up Tube Screen) as well... in a Pre-Emptive Strike to ensure that the "New" Motor is being given every single chance to behave itself once it's installed and is Up & Running.