Welcome! I am sure that others will have helpful advice to share; however, I thought I’d give a quick answer to your last question:
The AAVSO uses its own observer code system, which automatically assigns you an observer code based on your name. AAVSO observer codes use only letters. So, you won’t be able to match your MPC Obs code exactly. However, you could include your MPC Obs code in the “notes” field of your observation.
You can submit your measurement using WebObs. Here is the link:
If you don’t already have an AAVSO observer code, then WebObs will show you where to get one. Otherwise, you can submit your observation using the “Individual Observations” or “Observation Files” links.