help

So coming home from work the engine started misfiring and the Service engine light started blinking five times in staying on for five seconds and then blinking another five times in series. The car started writing very rough and stalled out every time I came to a stop which was not normal function for vehicle. Made it to the Toyota dealership. After paing the Service fee they told me it was possibly spark plugs, ignition coil pack, and an O2 sensor not functioning. I just changed the spark plugs and ignition packs three months ago. So I took the car home put new spark plugs in and a new ignition pack I ordered from Amazon and put it in cylinder for (which they told me at the Toyota dealership) and installed a new O2 sensor myself. Disconnected the battery to clear any trouble codes and restarted the engine. The problem still exists. The trouble code they gave me at the dealership was.p0304, p0138, p0110. The car is still miss firing and Service light keeps blinking.

The car has 164,000 miles oil change in regular intervals in all maintenance done by myself which I feel very confident and handling. I do not wish to take it back to the Toyota dealership so I was wondering if anyone has ever had or knows what the actual problem is cause I cannot keep spending money on a problem like this. Thanks for any help Ryan in DC