With no other info to go on (I consider location with some fluids):
Oil: 10W-30 for mild climates or 5W-30 for colder ones works for most folks this time of year.
Trans: Mercon of your choice. Some like synthetics (I do - I use Redline D4), while some prefer conventional Mercon.
Pumpkin: Your call. The spec is an 80W-90 weight, IIRC. I also run synthetic here (Redline) but it's your call. In racing, this recommendation can get modified. Friction modifier is also required with most fluids (some synthetics claim to have a modifier already in the fluid). Check with your fluid manufacturer.
Plugs: Autolite 25's are the stock replacement plug. Motorcrafts work just the same. STock gap spec is 0.052" - 0.056". You might need to buy a larger plug gapper if you havent run a car with the large gaps before (most gappers stop at around 0.045"). I'd not recommend Platinum plugs in any case. The plugs listed above are coppers (cheapies).
Gas milage: Fill it up, zero the odo. Drive it till you've got some miles on it. Fill it up again. Take the miles since the first fill up (188 in your e.g.) and divide that by the gallons it drank during that interval. E.g., 188 miles/10 gallons = 18.8 mpg.
The noise will require more info from you.
The stock 65 amp alternator is easily overwhelmed with any accessory load. The 3G's 130 amps are a nice jump and keep the lights from dimming at idle, etc.
Good luck.