Another good second plane first build is the SkyShark Fantasy. Can be tail dragger or trike http://www.skysharkrc.com/fantasy.htm .

The GP P-51 is a great first warbird. It fly's more like a sport (actually uses the same wing form as the Ultrasport).

For my first warbird, I wanted something a little different, not just another mustang. You should really check this kit out, easy build and very good flyer (more like a warbird than the GP P51).

http://www.redstarrc.com