How do you change the spark plugs on a 2007 Toyota Tacoma?

It is here

https://www.google.com/search?q=1996+Toyota+Tacoma+4+cylinder+2.7+Litre+firing+order

..

It could be a worn valve seal or even worn piston ring allowing oil to enter the combustion chamber from the sump. Check if your exhaust is blowing smoke when engine is warm.

check compression, check valve clearance, check injector for properly working, check for vacuum leak around this cylinder.

Obtain a Hayne's Repair Manual. They go over spark plug replacement.

i would check the injector the diagnostic machine can only read misfires and what cylinder its on not what causes them see if the #4 injector is getting power or if its clogged

Possible causes for a misfire:
Spark plug
Spark plug wires
Weak or bad coil
Dirty or a bad fuel injector
Low compression in cylinder
This is a case of testing and process of elimination. Have them all tested to find out which one is the culprit. Change the plug and wire to a different cylinder, if the misfire happens in that cylinder, you'll know it's either the plug or the wire. Without doing any testing, it's hard to say what the cause is.

Changing the spark plugs is a pretty easy task. The spark plugs run along both sides of the engine, 1 per cylinder. (3 on each side) You can easily identify them by the plug wires running to them from the distributor. Pop off each plug wire, (1 at a time) and replace the spark plug. Once you have replaced the plug, replace the plug wire. This ensures that you dont mess up the sequence of the wires which determines which cylinder fires at what time in the cycle. VERY important not to mess up the sequence. If you should happen to get the wires mixed up, look online for the firing sequence for your vehicle and engine.

Locate the spark plug cover on the engine.On some Toyota Tacoma engines, the cover is across the top of the engine. On others, it is along the side 4 cyl. Remove the cover to reveal the ignition coils and spark plugs wires. The spark plug wires are plugged directly into the engine and the ignition coils are in the tip of the spark plug wire.
Remove the coil and wire from the spark plug. Twist and pull the plug out of the engine. Remove the spark plug from the cylinder well with a socket extender and socket wrench. Turn the wrench to the left to unscrew the spark plug from the engine.

Discard the old spark plug and apply a coat of anti-seize compound to the threads of the new spark plug.

Insert the new spark plug into the socket. Use the socket and extension to screw the spark plug into place.

Return the ignition coils and spark plug wires to the engine and turn it to lock the plug in place. Repeat the entire the process with the remaining spark plugs.

Replace the spark plug cover when all of the spark plugs are replaced.

Good luck and hope this helps and The spark plug tension may range between 11 and 15 foot pounds, depending on the size of the spark plug. The correct tension is indicated on the spark plug's packaging.

24 mpg on the highway is actually pretty good for that truck. at 48000 miles and being 3 years old its time for plugs, air filter, and fuel filter if available. thats cheap maintenance for now. but if very self conscious, run some fuel injector cleaner first, then change the plugs, because any octane booster or fuel injector cleaner can run the risk of fouling out a plug, by creating a hotter spark then what, normal gas does. the burn is hotter.

P-0304 indicates number 4 cylinder misfire. Are you using Toyota parts dept spark plugs? More often than not, non-toyota plugs make the v-6s run poor, right out of the box....
Try this:With the engine running, pull the connector wire off of the #4 injector. Note to see if there is any change with the idle quality. No change? You may have a bad injector.