Spark plug coils are pretty easy to change, but don't just assume that it is causing the issue. There are many things that can cause power loss. Some of those things won't create an engine light. You are in luck that you have an engine light. Your computer records the fault and only displays the engine light.

Here is what you need to do: Find an automotive shop or parts store that will use a scanner to read the fault code. Call around, some will do it for free. It only takes a moment to read the codes with a scanner. The car's computer measures the tolerances of many parts and sensors. Any one of these components or sensors that fall out of the tolerances will store a fault code in the computer. Whoever scans your car can look up the fault code to find the component or sensor that is out of tolerance. From there, you can choose to replace it yourself or get it replaced by a mechanic. Once the part is replaced, follow the procedure in the manual to reset the engine light.

I hope that helped.