well, you don't really have to learn about the make up of the battery, just how to charge it. you can post a pic of the stock charger so I can be sure, but id assume it uses just the white balance plug on the lipos to charge them. This means it will balance charge them.

A imex b6, thunder ac6 and nearly all decent lipo chargers will use the main plug (red one) and the white plug. They pump the juice threw the red plug and balance the cells threw the white plug.
And there are videos on youtube showing how to setup most lipo chargers (make the selections you want threw the menues, ect)

If you upgrade to batteries with a higher C rating or higher MAH rating, you don't need to upgrade anything. The voltage will still be the same, just you will have more runtime and a bit more punch.
You would only need to upgrade the ESC / motor if you wanted to run 6s (or a pair of 3s packs in series) and honestly the XTE is not designed for that. It will work, but the frequency of breakage due to higher speed and much greater motor torque will happen. Stick with running pairs of 2s lipo packs for now. But you can get a pair of 2s 5000mah 30c (or 40c / 50c) packs to increase your runtime.

Due upgrade the steering servo. a metal geared servo with at least 200oz of torque will work better. It is not that the stock servo wont work, just the life of them is hit-or-miss. ive had a redcat servo last a year, while others failed within a couple of packs. So it is a good idea to buy a better one and have it on hand, so when/if the stock one dies you can just slap in the better one.

Redcat manual are generally poor. It is one of the downsides with the brand. when you pay less you always get shorted somewhere.

this video might help some: https://www.youtube.com/watch?v=Jb3v6l21nwU