1994 Buick Century Engine misfire

This car has been driven very little over the last year or so (probably under 2000 miles). When last driven, approx 3 months ago, it was firing on all 4 cylinders. Upon latest use it had an intermittent miss on probably one cylinder. I put a can of Heet in the gas and noticed little or no change. I also put in about five gallons of gas at that same time. I've driven most of the gas out of it now, so I changed the fuel filter (no improvement, and I observed no debris coming out of either end of old filter). I changed the spark plugs (the old ones looked like they had a million miles on them- slightly oiled and electrodes nearly eaten through). Miss consistently became worse and is now nearly constant. It will occasionally fire on all four under no load- very rare. I determined that cylinder #1 was culprit and changed that plug wire. Definitely gets white-hot spark, observed with plug removed and grounded. I'm guessing clogged or bad injector. How do I test, clean, or change that injector? I've run two bottles of Lucas fuel injector cleaner through at this point. I'm hesitant to provide my credit card info at this point, but I intend this car to be my 16 year old daughter's first beater car, and will absolutely compensate anyone (fairly) that genuinely helps me fix this thing. Thanks, Jace