You'll love the UCD. They are great flying planes.

Number one upgrade I think is the pushrods. Go carbon fiber from Central Hobbies for the best. Next best would be to go with 4/40 pushrods.
Number two upgrade is the landing gear. Many reinforce it before they ever fly. If you land it soft (all the time) you won't have a problem, but if you hit it hard it will break out. On my last 3 I flew it stock and didn't have a problem. The first two I broke the gear. I fixed it after it broke.
Number three is to make sure you open the cowl waaaaaaaaaaaay up. You need a lot of air in and out of this thing to keep the engine cool.
If you fly off grass you'll want to use bigger tires. At least 3".
The best power supply is a Saito 82. Second is Satio 100. Use a 14x4 on the 82, a 16x4 on the 100. This plane deserves a nice 4 stroke.
Use good high torque servos. It will fly better if you do. I like the digital 5645 on the rudder and elevators and 5625 on the ailerons.
Best mod...but the UCD3D sticker on upside down. That way when you do a low inverted pass you'll be able to read it.

This plane is one of only a very VERY few planes with will do a rising inverted flat spin. Neatest 3D move I've ever seen. Of course it will do the other things well also. Waterfalls, hover, flat spins, blenders, and just having a great time. It's worst traits are KE and Harrier.

Sit back and enjoy this plane. It's truly one of the greatest planes out there.

Thanks
Barry