Cool OK first let me applaud you for going the kit route something you seldom see these days but I do want to caution you that given what ever amount of time you estimate it is gonna take, it will be at least three times that figure. One of the fellows I am currently mentoring a bit also wanted to build but in the interest of time he purchased several other airplanes already flying locally (ones he could watch fly before purchase) and got started with those. That being six months ago he is turning into a fine flyer. So recently I bartered with him for a new Senior Cadet kit (I hate selling).
Anyway he is doing great now and the fuselage is finished and he enjoying the learning process. The TT 42 GP should work well never had one of those in my hands but have worked with many of the "pro" version of the TT's and its a fine engine, I suspect the 42 is as well. For the radio system I am primarily a Hitec user with a sprinkling of futaba
So can't offer anything on spectrum.
If this airplane ends up being your first trainer may I offer up an opinion that wheel pants are a really bad idea as they will take a beating and usually that type of fluff on a trainer does not last long. I can however offer up a direct answer to your last question as to using the Great Planes Cherokee arf wheel pants on the wire gear on your Eagle. Since I happen to have on of those Cherokees in my stash pile waiting for a little refurbishment (one that I bartered for
).
Most low wing airplanes with wire type gear feature a gear leg that is vertical from the bottom of the wing to the wheel axle, now if you look at the wire gear on your Eagle you will see that the main gear leg slopes outward and downward to the wheel. Most methods for a low wing wire gear to hold and support a wheelpant are not practical to support a wheel pant that slopes away at a forty five degree angle. So yes most any fiberglass or plastic pant can be adapted but you will have to fabricate your own mount system.
Get involved with you local RC club and start networking now. They usually are an invaluable resource in many ways beyond just a 'runway'.
John