depends on how the walls are removed.. if you want continuous new ceilings then that adds dramatically to the cost and wide doorways would be cheaper but not sure it's a good ides to lose a bedroom.. what are your long term plans for the house?

happy with either continuous ceiling, or large openings. ideally flush walls if possible on at least one opening.

will convert the current lounge into master bedroom, and have open lounge/dining area, utilising the waisted hall space.

always depends on surprises eg is there any asbestos in the walls and floor (with asbestos add extra thousands) and think about how furniture will be arranged ....would removing the whole wall give you any better furniture arrangements and consider moving the new master bedroom door to open in the bathroom hallway (and close up the other two doors but how would you patch the walls, floor and ceiling if the whole wall is removed...what are the walls and ceiling lined with and are there plaster cornices and decorative ceilings?... you will need an electrician to remove the existing wiring to make it safe for demolition and then come back later to install the new light switches and good time to add an extra power point or two... say two half days about $1000, a carpenter to safely demolish and rebuild anything that needs extra support, fill in and open up new doorway, rehang recycled old door, add architraves and patch skirting boards...maybe two days if you can help with demolition and rubbish removal and cost say $2000, a plasterer to repair plaster walls and ceilings say $1000 although a carpenter can usually do minor platerboard repairs and maybe $500 to repaint the new rooms if you do all the work yourselves plus whatever floorcoverings need to be replaced ...so expect about $5000 - $10,000 assuming no major problems ..but only a quote for your job will be sure

This will actually depend on the type of construction of these walls, roof and floor. Best that you consult a local builder who can then give you a clear idea of what work needs to be done and a the cost to do it.

Hope this helps, Malcolm