>>Anyone know how I find out what kind of gas is in it??
There should be a sticker on the bonnet slam panel giving the type of gas and the charge mass.
Failing that, look for a charge point - if your's is a Diavia after fit system, these will be in the nearside inner wing. Take a plastic cap off, and look at the fitting. If it's a bit like a tyre valve, it's R12, and if it's a larger, snap lock fitting like ebay item 310137483310, then, it's R134a.
Don't be tempted into filling the system with gloop, go and see a proper air con specialist and have the job done properly.