Not the op, but I recently added a 50amp circuit for an oven to my ‘50s era house (currently gas). There was a crawl space behind the kitchen, which was not insulated. The hardest part was getting the conduit measured, bent and attached to the house to go from the electrical panel to the attic. Then I drilled holes in the studs for the wire and fished it through and insulated the wall.

Worst case, you have an insulated wall that you need to tear apart. For pre ‘78 houses, do a lead and asbestos inspection before starting work. You would have to tear down drywall/rocklath, tear out insulation, cut holes in the studs for wires, put up new insulation, new drywall, and mud/paint the walls. You could do that in a weekend assuming you have the materials and tools starting Saturday morning.

Looking forward to a reply by op because I suspect their house is above 200amps because of the appliances and cars they have.