DrAlex

AS and VX have different upgrade policies - I would highly suggest spending some time in the Alaska Airlines forum familiarizing yourself with the various pros and cons of the program. I myself am pretty new to the game, so I spend way too much time reading about all the business. But, as a minor Avgeek, it's better use of my free time than Facebook at this point... There are a lot of intricacies to the program - especially about redeeming international awards on partners.
The upgrade process for AS is pretty straightforward, but does require the rare prodding at the gate. As a Gold MVP, many of the fare classes qualify for premium class upgrades at booking and you can book exit rows at booking as well. Upgrades to first would depend on the route, but I would imagine you'd be close to 100% out of SJC, but less so out of SFO (especially with all those transcons).
The VX upgrade process is more nebulous and is suffering from neglect and the integration process. Elite AS members (the VX Elevate program has already been assimilated) flying alone can request an upgrade to Main Cabin Select when booking (or just after if booked through AS). When traveling with a nonelite, VX Twitter seems to be the best to request the upgrade at T-24. There are no first class upgrades on VX - you can buy up (and that's cheaper once already upgraded to MCS). On April 25th, VX gets fully incorporated into AS and the upgrade process goes over to the straightforward AS process.
I've only flown VX thus far this year and I haven't been upgraded to MCS - both flights were full and I'm a lowly MVP.
The other thing you might want to consider is pairing your AA status with AS for international travel as you can still earn & redeem on international AA flights. Just a thought.