Are all the major exchanges basically exactly the same or is it worth finding out the best one for you (what is the best one?)?
Also can an exchange such as Mt.Gox be trusted with my money in an account or are their any problems with that?
Thanks in advance.
Well, you're mostly right here. Still there are some different types of exchanges through not many. www.otcexchange.net
is an example of what we've done in order to provide bitcoin community with more options. It's based on peer-to-peer concepts so there's no deposit-trade-withdrawal scenario at all. Thus it could never end up with scam like russian btcex.com did, or a tremendous rollback that mtgox shown to us just recently.