Driving a 160,000 mile '99 Camry and I'm aware the first iteration of the 1MZ-FE (non-vvti) is notorious for having sludge buildup. How can I tell if the issue is already present? I am planning on doing some upgrades that include the optional TRD Supercharger from when the car was new and I want to make sure the engine is healthy enough for the upgrade. Not really trying to open up the internals unless absolutely necessary. Car has had regular oil changes every 5000 miles for the last two years but has been sitting for about 5 years prior.
If your oil filler is on the top of a rocker cover then you can take your oil cap off and look inside with a good flashlight. A dental mirror can be useful for this, as can a flexible camera if you have one. You should be able to get an indication from an inspection, if you see sludge buildup then it's a good bet the rest of the engine is sludged up too. If all you see is shiny sides then it's an indication someone has de-sludged it.
Another good check is to empty your oil, drop the pan and have a good look from underneath. Taking off the rocker cover is also desirable, it's more invasive but that's a place that sludge typically likes to hide.
Before you remove sludge you need to consider the possible drawbacks. In older, higher mileage engines seals break down and sludge can act as a barrier, keeping the engine from leaking, de-sludging an engine can remove that protection.
Lastly, before you stick a supercharger on a 23 year old engine with 160k miles on the clock you should consider the state of the seals and gaskets, and whether they will stand up to the pressure. You could invest a lot of time and money in upgrades and end up with blue smoke billowing out from your engine compartment. If you do want to put performance mods on this thing you should consider a rebuild.