basically, yes. But mastering isn't meant to do huge changes to the overall tone or loudness, it's not meant to be a fix for problems in mixdown.
This all boils down to getting your whole mixdown right. I'd suggest while creating the tune and it's sounds, simply ignore the master level, just keep it from distorting (going to red). If you have to turn it down a few dB then go ahead (despite what I said earlier), you're not going to destroy the track by doing so. At worst you'll reduce your dynamic range by a bit or two but there aren't many people who can hear the difference.
Then when you consider the track otherwise finished, it has the structure you want it to have and the sounds fit together nicely, let it sit there for a few days or even weeks. Then when you open it up again you'll hear things that you might have ignored earlier or spot weaknesses in the mix. This time, focus only on getting the levels right, adjusting EQs, redefine compressing levels etc. Now you could also focus more on getting the master peak within -3dB.
Practicing some home mastering isn't that bad either if you want to play it out in a club or whatever but don't want to shell out 30£ for getting it mastered. If you're not sure what you're doing, there's nothing bad in using presets for master bus compressors, limiters etc. It's a great way of learning what you're really after.