• Both PCM and PPM are encoding methods running in the FM modulation mode. One is a bit more interference resistant than the other, but the standard PPM is the one 99% of us use for glow engines.
• If you DO use the PCM mode, you should make yourself aware of the advantages/risks of programing certain fail safe settings and in some cases not to use them at all (That's a whole different discussion that you don't want to start here...).
• If you choose a computer features radio the 6XA series is a very good one, but also consider that if you get a low end set like a Tower 6 channel with the standard servo airborne pack and later decide to upgrade, the only thing you make redundant is the TX. Comparing the cost of a new basic 4 or 6 channel system to an airborne pack such as you will buy for your second plane (oh yes, you will end up with many ships at a time ) the TX is a small price. Besides, you will want a second TX around sooner or later, so nothing will be wasted.
• I second the GP-.42 choice, it's a neat little engine to begin with. For my 2 cents worth, avoid the OS-LA.40 like the plague, but some like them... If you're in the higher $$ range, the Tower Hobbies .46 BBABC is a great performer for the price.

Still to come are the top end ships and all those pretty 4-strokers and gas engines... Are you sure you want your wife to know what it will all cost?

quint