mstateglfr 

To learn, I used youtube, Sheldon Brown-Bicycle Technical Information, and Home Page | Park Tool
Combined, the 3 sites will answer any question you have and show you video how to do something or have still pics of the process.
I basically googled a bunch. So 'remove crankset, parktool' for example. That would lead me to park tool's website where they walk you thru removing multiple types of cranks.

As mentioned earlier, you need a few specific tools. There is just no good and realistic way to remove a square taper bottom bracket besides the specific tool. Cone wrenches, to me, are necessary. You can actually get double sided park tool cone wrenches(so 2 sizes for each wrench) for $6 or so online.
One other specific tool you will need is a cassette lockring remover. Its made to fit in the cassette and turns it to allow you to remove the cassette on the back wheel. This is necessary to both clean and regrease the rear wheel hub bearings.
You could clean the chain without removing it, but it wont be very clean. Again, thats a tool which is specific to the job.

There are about 4 tools at a minimum that are specific to bike maintenance. The rest of the bike build is mostly bolts which connect in standardized ways.
4 tools- crankset puller, chain breaker, cassette lockring remover, cone wrenches.



My advice, if you choose to tear the bike down, is take pictures before you do something. For example, if you remove the fork and headset to clean and regrease the headset- then take pics so you have an easy reference for what stacks above or below what. Another example is a wheel hub. There are multiple spacers and threaded parts on each side of the hub. Take a pic so you can easily reference the order they go back on. This was very helpful to me until I got the hang of it.