I have a 3.2 auto, and having dome cambelt and covers with a service (new GM plugs etc) at 68000 miles I noted that one of the coil packs had rusty deposits on a spark plug 'boot'. As I didn't have a replacement to hand the original coil packs were used. Within a day of doing the work it developed multiple misfires etc. Got the codes out using the pedal trick and got the 0300 codes and others relating to misfire were present. When it happened, I was driving at low speed and the EML flashed for about 10 secs and then stayed on.
I replaced the coil packs on both sides and normal service was resumed....
There was no oil in the plug wells, and it would appear that prior to me purchasing the car in 2007 the engine had been steam cleaned/jet washed (very clean and dressed up with a back to black spray). The water had obviously caused the premature failing of the coil pack.
I am in no way advocating the replacement of parts without correct and complete diagnosis, however it would appear that the symptons you have described are identical to mine. Unfortunately miggys are now older vehicles and are starting to show their age, by parts failing, that will require replacement.
On old car with distributors and contact breakers, ignition components (points, rotor arm and distributor caps) were service items to be replaced at regular service intervals, sometimes yearly.
The coil packs on the 3.2 replaced these ignition components and do not require replacement at service intervals. However they do fail and will need replacing at some point in the vehicles life especially if it has completed a significant mileage which I would suggest in excess of 100000 miles is. Remember as well it is a second hand vehicle and although you may have a service history you do not know how it has been maintained (service records can be ficticious) and you must expect components to fail and the associated worry that goes with that
Good luck