Every time I have my bike on for more than 10 minutes, the coolant reserve starts boiling over, blowing off the little silicone cap, and spilling the coolant everywhere. Also, my bike now has a difficult time starting--it seems like the battery is fine, but the engine just doesn't catch. These problems all started on the same night after work. In addition to these issues, oil started leaking on the tailpipe, causing smoke. When it wouldn't start initially, I had the clutch on, and tried revving it over and over--so I was wondering if I had somehow flooded it, and the oil leak was because of that somehow. Anyways, I am traveling to Argentina in two weeks, and don't have much money to spend on fixing it, so any advice would be much appreciated!

The oil leak down onto the pipes is the head gasketleaking at the oil return draind on the underside of the head and I would have an educated guess and say the other problems are also from a leaking head gasket.
You could try retensioning the head but as you are going to Argentina then a proper fix is called for by replacing the gasket.

I had a similar problem with coolant leaking into the cylinders and causing no-spark.
The headgasket is replaced, though I could not see a clear cause on the gasket. Still awaiting first start. Fingers crossed.
The K engine is built to do this easily, though a fair bit of the engine needs to be removed.

If you don't have a factory book:
Drain oil and coolant
Remove Engine covers, radiator, airbox, exhaust, and plenum chamber. Basicall everything that is in the way of getting the engine cylinder block off the bike.
Remove right-side frame-to-engine bolt, 8mm hex.
Get the timing chain off. Might need some encouragement.
Remove cylinder block. 10x 8mm hex bolts. Best if two to tango, you DON'T want the block to fall off.
Clean the mating points and mount new gasket. Some may suggest a sealant. I did not use this.
Torque cylinder bolts in sequence from center out. Once you feel resistance, you should tighten only half a turn on each bolt until you reach torque value, to avoid warping.
Get the rest of parts back on.