Hello, I apologize in advance if any of the questions I ask are silly.
First and foremost I love biking, used to BMX a lot as a kid (Redline 180 mini I believe) but due to unfortunate family related circumstances, I fell out of it and just continued to bike. Somewhere along the lines I stopped biking entirely and just got fat.
However over the past year and a half I started riding again, love re-kindled, 10-20 miles 5 times a week. Ended up losing a bunch of weight (with the correct diet, 195 to 135 pounds, 5'5) after going through 2 "wally world" bought bikes within a period of 5 days I ended up investing 300 bucks into a k2 Astral 2.0.
Introduction and story aside I'm starting to notice some wear (Rough spin when rotating the chain backwards, losing speed and non-smooth gear changes, more resistance than usual on the higher gears) despite riding for a while my experience with replacement and maintenance was very basic (http://bmxmuseum.com/bikes/redline/30634#.UTmvcFfDt8E the only bike i actively maintained while I was a younger) and the bikes I would ride on the road were cheap wally world mountain bikes that I quite frankly did not care much about and weren't very fun to ride.
The Astral seems different though, I knew that I would have to take care of it at some point and admittedly I have only done basic wipe downs as nothing in regards to performance has changed over the past 4-5 months, despite constant 50-65 mile weekly rides. Until now anyway.
Specifications are as follows;
FD - SR Suntour - FD8-XCC208
RD - Shimano RD-M360, Acera
CS - SR Suntour-XCC 28/38/48T w/Guard
Gear shifter - Shimano ST-EF51, 21 Speed
Cassette - Shimano MF-TZ21, 13-28
Now the obvious here is "Do more maintenance aside from wiping it down"
but my primary concern is replacing parts, maintaining specific bits and pieces of equipment. Identifying problems. Now I'm not entirely sure If I'm overthinking things, maybe I should start worrying about more intense replacement aspects when I invest in a better road bike down the road.
I'll stop ahead and quit rambling, but I suppose the meat and potatoes of my question is this
"What are some basics and good things to learn once you've invested more than 300 bucks into a bike you ride on quite actively?" and "What sort of compatibility issues should I look out for when I do learn how to replace parts?"