All of the above, plus I would coat the rubber weather stripping & seals with 303 or Meguiars, as well as apply leather conditioner to the seats. A coolant flush would be good and consider changing the tranny, brake & power steering fluids when you get back.

I stored mine at a Porsche service center last winter, and they also propped the windshield wiper arms slightly off the windshield with balsa wood blocks to relieve the spring tension, as well as leaving the handbrake off, tranny in neutral with one wheel chocked ( manual trans only).

Having said that, I like 180's advice to sell it and get another one when you return. A lot can happen in 2-3 years. Good luck on the job assignment!