If you can get a good deal on the FX then I would say go for it. It's a great engine and will last you well past your trainer. There is only one problem that I didn't like on the FX's. The remote needle valve mount is part of the backplate of the engine. Any crash will usually break off that needle valve mount which requires buying a new backplate (~$15 + shipping)

I wouldn't really recommend going with Nitroplanes as your first plane. The instructions that are included with the planes leaves a lot to be desired, which isn't a good thing around somebody that has little to no experience in the hobby. Also, there have been reports of less than good customer service.

An Extra 300 is NOT the plane for a new pilot. This plane would be ok after you have flown 3 or 4 other planes first. But it's not a first plane in any stretch of the imagination. While you say you have flown but not taken off and landed, I would say that you haven't flown yet. My recommendation is to get a good trainer and find a good instructor to teach you to fly properly.

I've put together a list of planes that make good trainers and second planes. All of them on the list are proven planes that are well suited for successfully letting students learn to fly, or advance to a second plane. Check out the list here
[link=http://www.rcuniverse.com/forum/m_4537845/tm.htm] Looking for a trainer- what's available. (Updated 12-20-07) [/link]

Hope this helps

Ken