first off, for anyone needing help on this game, id advise going to the playstation forums. someones probably already asked the question before you, if not, the community is great and will help any way they can.
anyway, the game itself is immense. it may take a few hours to get into it, you feel rather weak until you get past level 10, its all a bit much to take in at first too. but when you get into it and realise its epicness (yes, thats a word) you will be blown away.
the beauty of this game is the openness. you could complete the story mode and easily miss half of the game.
regarding this version, the expansion packs are selling for £8 each on the PSN, so this is a bargain! you can even go on the PSN for a trailor on each expansion to see what to expect.
if i could give 1 peice of advice it would be to take your character, pick a direction, and walk in it! you never know what you will find, but you WILL find something. and it will probably be great!
get on the internet too, you can find maps with points of interest and guides etc. if your after the platinum for this game its essential.