2011 90 Mercury 4-Stroke switching a 25 inch foot to a 20 inch foot.

I need a 2011 Mercury 4 Stroke outboard lower unit spe******t who can tell me what I need to do with my lower unit.
Here's the current state of things.
I have a 2011 Mercury 90HP Four Stroke EFI with a 25 inch Shaft.
i have already bought all the Mercury Parts needed to complete the job.
1- 20 inch shaft
1- Stud drive shaft housing
4- Studs
1- wear sleeve assembly ring kit
1- shift shaft
1- seal kit
- marine grease
my new boat is made for a 20 inch transom outboard.
So, I need to obtain the correct instructional material to remove the 25 inch lower unit off, remove the 5 inch adapter plate, & replace the following parts which I already have purchased to correctly change out the parts to make my outboard a 20 inch foot to match my transom.

I would a Mercury professional that is familiar with my particular motor and what is needed to do the job I am trying to do. I need either,
A.) someone who can tell me it can't be done without a bunch of specialty tools, a experienced Mercury Mechanic, & a Mercury Shop manual.
B.) I this job isn't that much of a specialty job,i would like to obtain either a Mercury shop manual showing the process being down professionally so I can determine if I have the mechanical ability, & correct tools I need to complete the job correctly.
C.) either a video or written tutorial showing the step by step Process being started & completed.
I am not sure there is a manual that addresses doing a lower unit parts conversion like what I am doing.
Thanks,
Gary

Raise the motor 5" or go buy a 20" shaft motor. There will be people who will trade you for a 25" as well. Changing 20" to 25" needs an adaptor kit, easy installation. Changing 25" to 20", pull the powerhead and put it on a 20" mid section and lower unit of a blown motor. So just raise it 5" won't hurt and easy as any installation!

I understand what your saying, but I already have all the parts to just swap out the parts and remove the 5 inch adapter plate. So I just need the instruction manual for my motor on how to do the job of switching the parts out.