CP-E Dual Cat Back

[Speed_J23]

So I received my cp-e cat back today, (bought off another member) and I was wondering what tools are going to be needed, what to look for any help is appreciated. Also am I going to need a new gasket flange since I still have the stock downpipe, the previous owner had it hooked up to a cp-e downpipe.

Thanks in advance
Johnathan