Maybe ask your CM to show you how she does a change? Ask her how often she does change? (How many wet nappies do you get back, that can give you an indication if you dont want to ask)
As for the MF boosters, they are rubbish. We used Hemp on the bottom, then a bamboo and a small MF on the top. MF squishes wet out when it's sat on, which wont help the leaks.
As for the shot elastic, I believe they're easy to replace, but I havent tried yet