Ok, so one thing to warn you about…
Assuming the conversion still works, you need to set up your XBL account, and load it up with XBL Gold time BEFORE you sign up for ultimate.
Once you sign up for ultimate, then you have to pay the normal price. Technically you can still buy XBL Gold time and it will convert, but it converts at the reduced rate.
That’s why you need to load up on the max amount that it will convert, of 3 years of Gold time, first… then upgrade to Gamepass Ultimate. That first time you activate gamepass, it converts gold time at 1:1.
Or, at least that’s how it worked in November.
I just checked, and it talks about converting a max of 36 months at the current conversion rate, but I’m not sure what that was… back in November, it was 1:1, but even then the “normal” conversion rate was less… so I don’t know what rate they’re doing during initial upgrade.
Make sure you know what they’re doing though, I don’t want you to get screwed by paying for 3 years of service if it’s not giving the significant advantage of the lower rate. I mean, gamepass is still a cool deal, it’s just not the crazy deal.
EDIT:
It looks like the deal is still going, based on this, which is recent as of December 17…
https://answers.microsoft.com/en-us/xbox/forum/all/upgrading-from-xbox-live-gold-to-game-pass/d619d709-6a62-4632-8f71-5a8ee88ea88b?auth=1
Which cites this…
Which says…
What happens to my prepaid months of Xbox Live Gold and/or Xbox Game Pass for Console or PC when I join Xbox Game Pass Ultimate?
When you join Xbox Game Pass Ultimate, we will apply any prepaid time you have on Xbox Live Gold and/or Xbox Game Pass for Console or PC toward Xbox Game Pass Ultimate, up to a maximum of 36 months.
For example, if you have 3 months of Xbox Live Gold and 3 months of Xbox Game Pass for Console already on your account when you purchase your first month of Xbox Game Pass Ultimate, you will have a total of 7 months of Ultimate on your account before you need to renew your membership.
So it looks like you want to make your account ( you can do this on PC or whatever… I still had my old account around from my 360 days)… then buy 36 months of gold time (I did this via amazon, but there are sometimes other places you can buy gold time at a discounted price, which would make it even crazier), and add it to the account via the web… then upgrade to ultimate. But again, check the small print for yourself, don’t take my word for it.
Good luck stormin’ the castle, Lee!