100,000 tune up…done,600.00 dollars later car wont pass emissions…some code 341. Now they want my car for the day to check ignition module/coils…would like to check things myself first, have no knowledge but willing to learn…any suggestions please 
Have a look at this: http://www.obd-codes.com/p0341
You’ll want a repair manual - the cheap ones are $20 at an auto parts store and often helpful. Autozone has even more bare bones ones online for free if you go there and register. It normally will at least help you find out where things are and sometimes gives testing specs.
In addition to a manual you’ll want a digital multimeter (also easily had for $20).