Measure one wire from each connector and multiply to find the amount of sleeving you will need for each cable. Then multiply the total by 20% so you have extra for mistakes. As for shrink you would want about 5.5ft of it.(This was my math for 15mm of sleeving per side of cable with 3 fans extra to sleeve with some extra incase of mistakes)
As for actually wiring it back up, the easiest way is to take one wire out and sleeve it then put it back in. That way you dont mess the wiring up.