Is buying an environmental paint, interior and rustproofing protection package worth it?
Generally no. Todays cars are much better than the ones years ago,but dealers still try to sell those packages because its extra profit. I had one car that the manafacturer recommened NOT to rust proof.
No. And the rustproofing package can do more harm than good. Application can require breeching areas that should not be breech and even clog vent holes or impair drainage paths.
But a good washing and wax job, which you can do yourself, is an absolutely good idea. And if you have wee ones a spray can of Scotchgard for the interior may be a good idea too.