A quick hello and a question or two

Hello all. My name is Rob from Chesham (BOV) and I've recently come back to flight sims after a very long break. Things have improved enormously!! 

I using FSX:SE with a PMDG 737 800, EZ Dock, and Rex 4 on a fast computer.

My questions are:

1. After a number of successful auto-lands at various airports, I've tried twice to approach and land at Heathrow: first time my plane went into a nose up stall from autopilot, (I was looking around outside at the time - that'll teach me!), I recovered from this but could no longer select CMD A but I could select CMD B. I cancelled this flight after not being able to change the route on the FMC mid-flight, which I'll need to learn. The second attempt ended up in a dive also from autopilot, with alarms going off all over the place. I had just attained VOR/LOC capture and had just pressed APP. I wondered if any of you knowledgeable people had come across this before, or whether there's a bug in the PMDG or something. Or maybe I did something wrong?

2. Is there a way of cancelling TOGA after it's been initialised - I was on hold short of runway and accidentally hit the assigned button on my joystick!! What fun! I held it on parking brake as long as I could, but had to cut in front of number one in the queue who was lining up on runway! I'm sure there must be a way of cancelling but couldn't find any info.

Thanks for your time, acronyms and abbreviations whilst difficult for a newbie are welcome as it's all part of the learning curve.

Happy flying.

Rob Padgham