you when you buy new ones. Check the U and eyebolts as well. Galvanized springs are better value.
Putting in new springs is a matter of doing the same procedure in reverse.
There should be a locating lug in the centre of the spring which should slip into a corresponding hole in the axle. Once this is done the U bolts can be locked back into the steel plate. Taking photos can help remember how it all goes together.