Fitting your self........ if you existing zorst has been on for a long time don't bother get someone else to fit. It will be a nightmare. The bolts sometimes need heating up to get undone.
If you decide to tackle yourself, get some new gaskets and some instant gasket stuff (not from Halfrauds cos its really expensive) and should take about an hour with two peeps
I asked the same question when fitting mine.........for the sake of 40 quid can you really be arsed? Get it to the garage and put your feet up