Upgrading cheap "cruiser"-type bike for commuting
This is what we call a BSO (Bicycle Shaped Object) -- everything on that is as cheap as possible, which makes sinking even modest upgrades into it not really worth it. For upgrading and tweaking, you'd be much better off starting with an old (but decent quality) bike. You'll likely come out monetarily ahead, and have better quality parts to make it easier to learn (e.g. derailleurs which stay in adjustment, etc.). Also, be careful if you're removing dents in a rim with a hammer -- its less safe than the proper tool (and be careful with spoke tension). 

If you want to do something to make it better for commuting, I'd limit it to maybe a set of bar ends if you want more hand positions or a better saddle. You already have slick tires.