repairing a TF700T?

i have a transformer infinity tablet that over a year ago stopped functioning.. in fact, i purchased it originally and it lasted less than a year before it stopped booting past the BIOS, ASUS forced me to pay 0 for repairs because it was rooted, even though it was a HARDWARE failure as they said the onboard storage chip fried.. so they replaced it after i paid them only for it to happen again.. not wanting to spend another 0 for something that would probably just fail, yet again (never buying ASUS again now) its just been sitting in a box

now i notice i can buy working motherboards for .. my question is would there be any soldering involved, any hardware locking issues or could i purchase a replacement motherboard, replace the old with it and fix my tablet?

Things to do before repairing (ROM, backups)

Hi,

my GPS stopped working so will have to send it to Sony to get it repaired.
Now I rooted the phone and installed the debloated 5.1.1 ROM.

Is it necessary to install the original firmware for warranty reasons?
And if so, how do to it most easily?
And is there a way to once getting it back I can easily obtain my current ROM with all APPS again?
I did a TWRP backup, and Titanium Backup of all apps, but I fear I will have to redo all the steps of the rooting procedure right?
Or given it's based on Sony's rom you think I can send it in as is?

THanks!
playagiron