cutting a new doorway

Hi, I hope some one can help me with my quiry, I want to cut a doorway through a single block wall which only suports the wooden joist for the first floor, but if I keep the doorway to a standard opening height of 6 feet 6inches, after cutting out for a lintle there would only be one block left above. 1 do i remove this level of blocks as well as the rest and build up on top of the lintle again or try to keep this row in place and 2 do i need to use acrow supports on both sides of the wall or not, and not forgetting 3 the opening i am creating is about 62 inches wide whal size lintle to i need to take the load