I learned to fly on the Tower Trainer and I think it's a great flying plane. I've been flying for 10 years and I still have my trainer, and it's got somewhere around 600 flights on it by now. You'll do just fine on it. As for the air cleaner, you don't need it. There is very little dirt and dust "up there" to get sucked in. Your cars need the air filter because your carburetor sits 1"-2" above the ground, but a plane at 100' doesn't need it. Maybe if you are flying off of a field that is all dirt you might need one, but I wouldn't worry about. In this case comparing the planes to cars is like comparing apples and oranges.

Hope this helps

Ken