I crashed my drone in salt water more than a year ago... obviously warranty repair was out, as it was pilot error.
On to e-bay... I basically purchased anything with a PCB which included a new IMU and 6 new speed controllers with their motors (3 of each type, CW & CCW),
even though technically, the pro RC guys around me assured me the motors are fine and will survive a water drop (wash thoroughly though with fresh water).
Buying the speed controllers with motors already attached meant I wouldn’t have to do any de soldering / soldering...
I purchased a new GPS board.
Of course, I purchased a new X3.
I did not purchase a new VPS, the original one worked fine - all other non electronic components were simply washed and left to dry (including the cables and the gimbal connectors etc...)
The whole disassembling and reassembling took around 15 hours or so spread over 4-5 days - with the correct tools, it was quite straightforward.
Took it out for a thorough test, using all my 6 batteries, one after the other - it was like new, no signal drops, no strange behaviour, and now I have it as my backup I1...
The parts cost around half as much as buying a new I1 (note this was about Nov. 2015) - so now, you will probably find more parts and cheaper on ebay.
I opted for new parts where possible, one of the 6 motors was a dud, I used DJI chat service and sending logs back and forth to figure out which one was the dud as I had installed them all at the same time - I guess it was one of the risks of buying off ebay... but still better than trashing it or selling for parts as I have reclaimed back it's cost from jobs already...
Good luck with it.