Our apartment (built early 60's) is woefully underpowered. There's
one 20A circuit to service the entire living room, dining area AND
kitchen. However the stove and oven have separate 220V circuits
and breakers.

We'd like to run a 220V air conditioner during our hot summers
by tapping off the oven's circuit (for reasons I won't go into here,
the oven is never used). The wiring has its own conduit and
junction box in an adjacent cupboard in the kitchen -- it's readily
accessible.

How much effort is involved in adding a few 220V plugs into this
junction box? Is it easy enough for an neophyte to handle?