Hi mate rear springs are pretty easy to change I've done quite a few myself, rather than explain how to do it and write up I'll post a link that shows you exactly how it's done hope that helps you mate.
I often find if people watch a video like this one it's much easier to understand, A note of caution don't use cheap springs like aftermarket type they don't tend to be very good. And also make sure that when you fit the springs you leave the waterways clear otherwise it just builds up loads of corrosion in where the water can't escape
https://youtu.be/rW8mFEaRMv4
Mick