They should not talk finances until after the assessment, and yours will never be in the equation at all, so don't worry. They should not just give the cared for a needs assessment, but also a carers assessment to you - you're entitled to it by law. There are no hard or fast rules on what you can expect - support often depends on how much money is in the pot for it, and every council treats respite weeks differently. But there is no harm in asking for things!
It would be a good idea to prepare yourself by writing down what you do on a daily basis, what he needs help with and what would really help you both. There are things like respite, a day care centre, carers, befrienders, telecare gadgets or OTs checking out your home and providing you with grabrails, shower boards or bed levers - whatever they deem necessary. The more you know exactly what you want, the more helpful it will be. Don't hesitate in starting high - you can always negotiate down a little. Tell it like it is and don't make things appear better than they are. They don't want to know the things you cope beautifully with, but the problems you need help with.