Go for it! Transmitters are designed today for multiple model settings so you can do just that. All you need is a flight pack. Like you said, match the frequency and manufacturer, but that's about it. From the sounds of it though, you only have a basic TX. The only issue this would raise would be that you can't save trim settings from model to model.
Not sure about the planes in question, but like woodsy said, check out the spads. For everything else you may need, I have always used www.towerhobbies.com. Many people have found other sites with free shipping what what not. I can't really help you there. Welcome back though. It's a great hobby!

Ty