whats wrong with my vaxhaull vectra 2.2 ls?

please anyone help my 51 plate vectra started to get the shakes and sounding very rough i was advised to change all of the exhaust. unfortunatly before i got round to this it ran out of fuel. changed the exhaust and now wont start why. suggestions were make sure it has a least 20 ltr of fuel in then it should go. it doesnt please help im desparate my husbunds had enough. hes going to scrap my lovley car im sure its simple as it was going before help help