About the possiblity of a vacuum leak or a plugged converter. The engine sucks in air to be mixed with fuel and this air/fuel mixture is detonated in the combustion chamber to apply force to the crankshaft which turns the driveshaft through the transmission. When you have a vacuum leak air is leaking into the intake somewhere causing a too lean mixture, hence bogging down and no power.
On the other side is the catalytic converter. It processes the exhaust after it leaves the combustion chamber. It burns what's left of the fuel that isn't burned in the combusion chamber. If too much raw fuel is left over it overtaxes the cat and will eventually block it.. If it is blocked it will cause back pressure. This back pressure will keep the exhaust from flowing out of the engine and hence, it will bog down and have no power.
They test the cat with a vacuum gauge which will read at 17 inches or less if it is plugged. Another way to check for a plugged cat is to take it loose and see if the engine runs better. A vacuum leak will also cause a low reading on the vacuum gauge. A low reading on a vacuum gauge will cause really bad mileage. So if it's too much air going into the motor or too little exhaust going out the motor it will cause problems. catalytic converters are so expensive because thy contain precious metals. A worn out or plugged cat is worth $50 to $80 at the boneyard.
The high and low beam is combined in the same bulb. To change a bulb look directly behind the headlight assembly and there should be a round cover to rotate counterclockwise to take off. After taking the back cover off you have access to the bulb. Unplug the wiring connector and unscrew the lock ring counterclockwise. Now the bulb should come out if you give it a good pull. It is a good idea to replace both if one is bad. They both wear out at pretty much the same rate. The bulbs operate at such a high temp that even a little oil from your fingers will cause one to overheat and explode. So, clean the glass of the bulb with alcohol before putting it back in and don't touch it..
Hang in there, things will get better.