Well, as in all cases of DIY advice, the standard disclaimer applies:

"If in doubt, don't!"

With that out of the way, let's follow the money...

The dealership really doesn't give a rip WHO pays for repairs. If it is warranty... dandy. If it is CP (customer pays)... terrific. As long as the dealer gets paid and the tech can flag his hours for the day everyone is happy.

In my experience the warranty approvals only get kicked back when there is a strong causal relationship between the failure and and some sort of neglected or bungled maintenance. For example; a catastrophic engine failure where the crankcase drain plug happens to be missing. That would get you some pushback.

However, if you show up with a failed shift solenoid... no one is going to bust your chops over the inability to prove that a qualified tech has inspected the ball joints and Cabin Air Filter.

Let's take a look at that list above and I'll tell you what my experience is WRT the things involved with a certified technicians inspection:

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Replace engine oil and oil filter 1 >>> Keep your receipts
Rotate tires >>> It shows if you didn't
Replace cabin air filter >>> Well, is it dirty?
Replace engine air filter >>> See above.

Inspect the following:
Automatic transmission fluid >>> Is it there? Does it smell burned?
Ball joints and dust covers >>> Check for excessive play and grease splooge.
Brake lines and hoses >>> Check for cracks and wetness
Brake linings/drums and brake pads/discs 3 >>> Measure remaining friction material... is it in spec?
Drive shaft boots >>> Are they cracked? Is there grease everywhere?
Engine/inverter coolant >>> Turns a foul color if neglected
Exhaust pipes and mountings >>> Are they loose? Is it loud?
Front differential oil >>> Check level, rub some between finger and thumb and smell.
Fuel lines and connections, fuel tank band and fuel tank vapor vent system hoses >>> Are they still there? Has OBD chucked a code?
Fuel tank cap gasket >>> OBD *WILL* chuck a code for this
Radiator, condenser and intercooler >>> Is it caked with bug guts?
Steering gear box >>> check for excessive play
Steering linkage and boots >>> Check for excessive play and cracked boots.
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Take a hypothetical failure of a CVJ (constant velocity joint)... In a new car such a failure would be very unusual. So the warranty auth center might send a technician and maybe a foreman out to take a second look. In this case they would be looking for dried grease slung around the inner circumference of the wheel well. They might also check for evidence of off-road driving or impact with a curb or parking block. Barring anything obvious, they will change the part and bill warranty. In this case no one in, or out or their right mind will compel you to prove that a molecular spectral analysis was performed on your engine oil.

Realistically, the majority of the time we ever kicked a warranty claim was due to extreme abuse of the automobile.

But like I said... and it should be repeated... "If in doubt, don't".

I've just, never had a problem in the last 23 years that I've been doing my own work.