Unfortunately I can't remember for sure but I'm fairly confident that you can remove the carb/blower with the engine still in the car. Your easiest option regarding gaskets might be to buy a complete VX gasket set assuming that they are still available, I don't remember off the top of my head which gaskets are unique to the VX. I think you could probably leave the inlet manifold in place when you take the head off but it may need to come off if you are getting the head fully refurbished. Apologies that I can't be much more help, I did rebuild my own engine but I don't remember a lot of the steps all that well now. If you think you are going to get more into it than just the head I'd consider dropping the whole subframe out.