Looks like it is ready for the takedown and cleaning ritual. As many of us have noted, this bike is a prime candidate for learning basic mechanics, with the added benefits that come with a re-build (i.e. running smoothly, being tidy, etc.

IMO, it would be more of a headache to try to tune it up as is - better to break it down, clean everything, relace what needs replacing (cables and housing come to mind, perhaps brake pads), then build it back up.

Remove the cables and housing first, then it is essentially easy work with some hex wrenches and the odd 8mm,10mm or 12mm open-ended wrench, phillips and./or flat screwdriver. If you aren't wanting to spend too much, you can forego removing the crank, BB and headset, though I'd recommend it to do a thorough job.
I'd also recommend re-packing the hubs (and headset) bearings.

Without too much effort and expense, that could be a really great bike.