As mentioned above, it's below/behind the alternator. Take a look down there with a light and you'll find it. If you do some searching, there are threads on here that clearly show the location on an engine out of the car.

Again, this isn't something you're going to be checking every day. Check it once (it's really not that hard to do), and as long as the system isnt leaking, you're good to go indefinitely. You shouldn't have to trust anyone to check your fluid levels.

 

I could not find the power steering, I took it to my Mechanic, he could not find it but said he knew it down there somewhere. My point is, IT SHOULD NOT BE THAT HARD TOO FIND OR CHECK THE POWER STEERING FLUID LEVEL. So far this 2002 Chevy Monte Carlo SS seems to be of poor original design. The hubs are a nightmare and designed too be a constant repair, the paint around the wheel wells is horrible, the valve covers are recalled, the driver's seat belt gets stuck behind the air bag, bad fuel pumps, bad drivers power window switches, tank pressure sensor, evap purge solenoid sensor and vacuum line, spark plugs difficult to reach; but the radio sounds great, looks great.

 

Be cautious not to overfill the Power Steering fluid, if you do it may take the seals out and then your going to have some leaks for sure, you will also notice a squeal as you turn the steering wheel.
Most likely indicating that it is dry.
I always check the work of the technician that works on the Car. The exception is when I am out of town and the wife has the work done.
I have had several of these guys do the work and not get it right, but that spans 40 years too. About 5 issues that were just dumb errors.

 

IMO if your mechanic can't find the power steering reservoir on a 3800, you need a new mechanic. That should literally be a 30 second job for a real mechanic to figure out where the reservoir is, and that's assuming it's a mechanic who isn't already familiar with the 3800.

If easy access to all fluids is really that important to you, I'd suggest you make that a top priority when you go to buy your next car. It really isn't that hard to get to. There are many cars out there far worse than a 3800 wbody for stuff like this.

A lot of the things you mention are typical maintenance concerns that can happen on any car. You have to consider that your car is 15 years old and isn't brand new. You could very easily have the same number of issues on a 2002 Nissan, Ford, Kia, etc. The only way to avoid that is to buy a new car. You'll still have a small chance for issues, but at least it won't be your responsibility to pay for repairs.

The hard part with a lot of this stuff is GM tries to keep the cost down on the new price of the car. They could certainly over design everything, but then that would not make them cost competitive in this market. These cars aren't like a semi truck that is expected to last hundreds of thousands of miles, it's pretty well accepted that 200k miles is about it for a cheaper passenger car, and even leading up to that it can be a slippery slope of maintenance items to keep the car 100% functioning.

A couple things you mention aren't really a design issue though. The spark plugs have a set location based on engine design, there is nowhere else they can move them. Power steering could certainly be moved, but it would be at the expense of something else, like the alternator or the coil packs, etc getting buried deeper down.