All the information you need are in the TMs that are listed here for free, download the first 8 to get you going.
The HMMWV is a 4x4 All-Terrain Military Vehicle introduced by the US Army in 1984 also know as Humvee. With over 300,000 units produced and in active service with 70+ countries as well as in civilian use.
www.nsnlookup.com
The parts TM 9-2320-280-24P-1 is where you will find the part numbers you need.
On page 5 (several pages under the TOC 'table of contents" you will find the list of UOC "usable on code" for you vehicle, you will need this to reference the correct parts.
You will see that a M997A2 has a UOC of B15, remember this number as you will need it any time you want to look up parts.
Now go to the TOC and scroll down to group 11 "rear axle"
You will see two listings "1104 Rear knuckle and geared hub assembly" with illustrations 150 and 151.
We know from experience the 150 is the 10K hub and 151 is your 12K hub, the two are clearly listed as used on "Basic/A1 OR A2 vehicles"
So go to illustration 151, you will have to scroll up to see the illustration.
The part you seek is number 11, in the illustration it is shown driven in from the inside but you will be driving it in from the outside.
So now scroll down the the parts list to #11
You will see this
11 PAOZZ 5330014563884 80201 534059 .SEAL,PLAIN UPPER.................. 1
UOC:BVY,B15,B20,B24,B25,C17,NNN
First you will see that that part is good for the UOC of B15, if there were two # 11s only one would have a UOC B15 listed, any part the does not have any UOC codes listed will fit any vehicle covered by the TM you are looking at.
So that part has a NSN number of 5330014563884 and a manufacture part number 534059, you can search these numbers for the parts you need.
Now you can look up any part number you need for your M997A2
Downloading and using the TMs IMHO is EXTREMELY important as it gets you MUCH more familiar with your Humvee and less dependent on others to get the info you need.
Nobody can remember all these part numbers so when you ask for a part number you are asking somebody to do the "booger head" work for you.
If you have trouble finding a number after actually trying to look it up yourself there are lots of folks here to help.
The meds are kicking in so I will tackle the labor part after my NAP!