Engine swap?

[Big Slick]

I am looking to do either 2 things with my kids TRX 90's

My son(8) has an 06'

and my daughter(6) has an 04'

The 04 has more grunt than the 06 does. The boy wants to keep the 06 body style, but wants the 04 motor.

I want to either swap motors or plastics.

I have read that it is a PITA to swap plastics, so I'm wondering how tough it would be to swap motors.

The problem would be getting the e-start 06 motor into the 04. Controls wouldn't be too bad. The 04 motor should be easy to put into the 06.

Anybody have any tips, tricks, secrets, or general advice to share?

Thanks!