To look after your forks without properly servicing them is pretty easy, after every ride clean and dry your bike and spray a little bit of GT85 or TF2 or any teflon or ptfe based spray to your fork stantions and around the seals, then wipe of the excess. Also check around your seals ever so often for cracks and wear, check your stantions regulary too for scratches or rub marks.
Most lower leg servicing to suspension forks work under the same principles: remove the air, flip the fork upside down, remove the damper bolts at the bottom or any gubbins like rebound dials then the bolts, tap the damper rods through and out of their seats, then tip the fork back up right, you should then be able to remove the lower legs of the fork and the oil thats left will trickle out.
Suntour rarely give service guidelines to what to do with your fork, it sounds bad but they normally make their forks as a kind of disposable item unless its their higher end forks. There are guidelines to what weight and measurement you'll need to use, but in a fork like yours its not such a problem using about 10ml-15ml of 10wt suspension oil in each leg because all its doing is lubricating and also giving you a little bit of damping. Make sure you clean the inside of the legs and then lubricate the seals (and the foam seals if you have them in your fork) with either a teflon based grease or specific lubricant like float fluid or judy butter. Then you can refit the fork with fresh oil.
There are loads of how to videos on youtube.