Check the cylinder head temp sensor in live data. See if it’s reading accurate. If it’s bad they’ll often read something like it’s -40 and be quite hard to start.

Do it once a year

What work was done? Some work warrants an oil change, like if you had a leaking fuel injector and it washed out the cylinder and fouled the oil, or something had to be removed that got some coolant in the oil.

Sounds like you have a bad battery. I’d test that first. A 1.8 amp draw might be normal for your car right away, some cars take 30-45 minutes to get the modules to sleep before you can accurately test for a draw.

Any codes? Did you use Nissan sensors? They are really fussy about aftermarket ones and often don’t work or last long, need to be Nissan parts.

Feel the hoses under the hood where they go into the heater core at the firewall. They should both be warm/hot. If ones hot and one cold you’ve got a plugged heater core. Can try flushing but heater cores aren’t uncommon on those to go bad.

About a wash, both aren’t bad at all

Use your owners manual and go by that, not what Amazon tells you

The fuel system will pressurize with a couple key cycles. How long was it apart? Just change the oil and start it up if it wasn’t any crazy long time. If it was months or something it doesn’t hurt to disable the ignition or fuel system and crank it to get the oil primed.

This is the flat rate system, the tech was obviously experienced and beat the book. This isn’t just a dealer thing and no you weren’t screwed over. I’m assuming You’d complain if it went the other way and took 18 hours and got billed for actual time. It’s how the system is and how lots of us get paid and how jobs are estimated/billed. If we beat book time we’re ahead of the game, if it takes us longer, we’re behind. Not saying I like it or it’s always fair but it is what it is. Warranty repair is even worse for the tech, usually about 1/2 of normal book time, so it takes experience and repetition to get good at it.

My wife had an 06 we sold in 2016 that had 360k on it at the time. We were second owners. Sold it to a friend that drove it even longer. I put a hybrid battery in it about a year before we sold it. Only other issues was a wheel bearing and the hvac blower fan went out. Put brakes on it around 180k miles. Definitely check on the hybrid battery, prices are super reasonable these days, especially if you can swap it yourself. The abs module/pump can get a little spendy, as can ac compressor work. Otherwise just inspect it as any other used car and should be good.

Not everyone reports to carfax anyways, I wouldn’t worry about it.

Should always diagnose rather than just throwing parts at it. Does it sound different than before when cranking over? Like faster than usual maybe? If the timing belt broke or skipped, there’s a chance it bent valves as that’s an interference engine. Other than that, check and make sure it has spark, made sure it has fuel/fuel pressure. Getting any codes?

Depending on location, most shops would be about $400-500 for that, maybe a little more in high cost places

All wrong, but. 3 is maybe a grey area. 3 I’m sure technically there’s a torque spec you should use, but it’s one of those things nobody does. Tighten and check for leak, but yeah by the book there’s a torque spec.

Best on the rear no matter fwd or rwd