How do you install a 12" VPI armboard for 12" Unipivot on a VPI Classic 3 - Thanks :-)

I'm considering upgrading my VPI Classic 3 turntable's metal 10" JMW UniPivot tonearm to a 12" 3D printed UniPivot tonearm.   I've some technical know how but want to double check how to install the new VPI armboard.  Any step-by-step guidance here and / or where to look for advice online is very much appreciated.  Thank you!  :-)
The easy answer was to send the turntable to VPI who were just great,

The VPI Tech moved the current arm base and installed a new black arm board under it to attach it and cover over the old 10" arm base holes.  I had checked beforehand that they could do this, basically on my shipping the turntable base both ways and no other charge(s).   

The VPI Tech also kindly did some undiscussed complimentary work: (1) cosmetic repair of two scratches on the base's black piano finish, (2) a replaced main platter spindle that the platter rests and spins on (it was just a  bit wobbly) and (3) added lubricant to the new platter spindle.  Wow! 

The VPI 12" 3D arm with Reference wire I had already bought was then too big to turn fully on the pivot with the supplied screw on azimuth weights.  Yep, smaller weights were needed.  VPI kindly sent me two sets of different smaller azimuth weights for free. The smallest size weights work great. 

So great service and then some....and the tricked out Classic 3 clearly sounds so much better - especially cleaner and more detailed aka more precise, smoother and a bigger soundstage!!!  Very happy and thank you VPI :-)
I might guess that at least some of the improvement you are hearing is due to replacing that “slightly wobbly “spindle.
Good point Lewm.

I would be extremely concerned about a "slightly wobbly spindle" and how it occurred to begin with?
Good point indeed.  The platter appeared to spin correctly, and there was no audible impact, despite the spindle's condition.  My guess is it happened the first time I re-greased the spindle.  When replacing the platter I hit the spindle a bit, rather than the platter going right on to the spindle.  The price of an education at least.  
PS Sorry I cannot post pictures of my VPI Classic 3 turntable with the upgrade to the 12" 3D tonearm as Audiogon does not allow photos.  C;est la vie!  :-(
The most important point is that you are very happy with your revitalized TT.
And it sounds like VPI stepped up as far as customer service is concerned which is great stuff.

As your name here says.... Have vinyl fun!
I am fortunately definitely having a lot of clearly. very improved vinyl fun!! 

I've also made two other VPI turntable improvements you may wish to consider for yourself :

1) Replaced the four VPI Classic feet with Isoacoustic GAIA 2's.
  GAIA"s come with three thread options, including the 1/4" 20 you need.
  In brief, their added vibration damping/control clearly gives my music      lots more clarity, detail and was!

2) The original 10" tonearm lift could not reach up and lift the 12" 3D tonearm, even after using an Allen/hex key to make the max adjustment.  Adding a pad or similar on to the lift arm was needed.  The solution?  To be found at that well known, high-end audiophile store...Home Depot...I kid you not...cut to size some double sided tape, place on the lift, then cut to size and trim the height of a 2" circular black rubber washer to go on top and you're done.  More precisely "Scotch" brand "Mount" 15lbs strong tape and an "Everbilt" brand 2" flush valve shank washer...yes, the washer is originally meant for a toilet but it works great :-)
I have just now added a $150 VPI Dual Pivot Tonearm Adapter to the base of the 12" 3D arm.   The net impact of this "upgrade" in my VPI vinyl system - with the Ortofon Quintet Black S - is it clearly sounds better.  Yeah!   All together, I'd say the net impact is around a +20/% or so improvement, with all the impacts/changes assessed together. 
There is:

1) More clarity and crispness between instruments AND more clarity and crispness between all the instruments and vocals,
2) Deeper, clearer bass end AND more detail in the bass sounds.  For example, I can now hear the strum "journey" of a bass guitar string and not just one broad or slightly smeared bass note.
3) A slightly less airy, floating top end.  The range of the top end is shorter.  To my ears the degree of this change is so much, much less than the improvements in 1) and 2) above.

Very happy I did this.  :-)