We are looking at purchasing a 1914 two story house. We had it inspected and it is structurally sound. The exterior was completely remodeled (insulated, sided, new windows, new roof and reinforced foundation) about a year ago. The interior needs work. It has the original wallpaper over lath and plaster walls in almost all of the rooms (especially upstairs). There are older cracks and staining on walls/ceilings. In addition, we are looking at updating the electrical upstairs as well as put in ducts to heat/cool the rooms up there too.

What would be the best way to correct these issues?

Thank you in advance for your suggestions.