I am slightly confused with your query.
Service is one thing and getting car washed is another.
Service @ 1,000kms is your Oil Change and check up your car which may include tightening of bolts here and there!
Getting your car washed at dealership or elsewhere posses similar if not higher risks i. e. washing engine bay.
So to answer your query: Take your car to Toyota Dealership every 5,000kms for service. They might sell you some unwanted repairs / service very courteously, to make money off you - but you may refuse them.
To answer your other query, as you are using the car, you may want to keep your car clean. In that scenario, do wash your car. The decision where you want to wash it is entirely yours. I personally don't think dealership provides car washes. They do wash your car pre-delivery and they might wash your car after service or repair (but that's very unlikely).
Last, not least I always suggest to analyse the suggestion and the person it is coming from. You might get a suggestion from someone who have absolutely no idea what he is talking about and ruin your car. In the end you are responsible as you acted on the suggestion.
Enjoy your car and welcome back to Pakistan!