First, if you only have 20K miles on your truck it almost certainly does NOT need brakes. These brakes last 80K plus under normal conditions. The grooves you see are normal.
Second, as 73shark said, you have wear indicators that will tell you if your pads are getting thin.
Third, if you do upgrade eventually, think larger, not slotted/drilled. Slotted/drilled rotors give you no performance increase (check photos of track cars,, no slotted/drilled rotors there). They look nice (I even have them on my Vette) but that is all. They also make pads wear more.
Speaking of pad wear,,, for all drivers,,,, if you see tiny rust spots on your chrome wheels it is far more likely that it is rusted brake dust than anything else. Remember you pads are semi-metallic and that metal rusts. You DO need to get it cleaned off the wheels though or it will discolor your chrome.
GL