The MAF - pop the hood and look on the air intake tube. It's right behind the air filter housing. There's a black plastic boxy lookin thing with a 3 wire connector going to it. On top, you'll see 4 torx key bolts that mounts it right in the air intake tube. How to remove it, I forget assuming you have a stock intake tube. I have a CAI so I'm rusty remembering how the stock intake tube is setup. Once every 10K miles is good enough for cleaning the MAF or every oil change if you'd like. That's what I do anyway.
The fuel filter you should do once a year but you can get away with every other year, depending on your gas quality and how much a year you drive.
As far as seafoam goes, this stuff ROCKS! makes a good smoke show too LOL! this is perfectly normal though. Read all about it here:
Daily Ride: 98 Ranger, 2.5 Auto, K&N CAI, Flow 40 exhaust, reg cab flareside, grey metallic, 235/70R15 Bridgestone A/T's
Other Ride: 05 Harley Electraglide, tc88, Screamin Eagle stage 1 kit. Chrome lowers, nastalgic bag guards, black cherry, 1965 Electraglide Emblems