Your real problem is gonna be access to the sides of the panel to get wire in and out since it's finished work (drywall and stucco). If you are up to figuring that out and how to run the wire then proceed. If I were in your shoes I would hire a sparky to run the 30 amp "dryer"outlet that matches your cord plug and also run a dedicated 20 amp 120 volt receptacle for the AC. If required another 20 amp 120 volt feed with a few receptacles placed for fans and shit.
Check the top two spaces on that sub panel (take the cover off) and make sure they are real and there is a buss bar behind there to stab into. sometimes they have a cover with more spaces than the bus and it's odd to fill from the bottom up. Just wanna make sure. You may have to take and consolidate some circuits using tandem space saver breakers (if available for your panel) 4 circuits into 2 spaces and free up two adjacent ones for the new breaker.
Here is a basic list of stuff you will need:
- 30 amp double pole breaker that matches your box type (Square D, Homeline, Siemens), it will take two spaces
- you can't use a single space with a tandem or "space saver" breaker as that's on the same phase when stabbed. They can however be used to consolidate 120 volt circuits to free space.
- #10 wire
- 10-2 if a three prong or 10-3 if a 4 prong, they don't count the bare conductor
- the cable type depends on how it's ran, non metallic (NM) for in walls and for exposed you can use metal clad (MC) with surface mount clips or conduit and THHN/THWN conductors.
- 30 amp receptacle that matches the cord end
- Surface mount metal box
- Cover for box that fits receptacle
- Connectors to enter the panel and the metal box (match the cable type)
