Pan gasket is reusable, and if you remove the drain plug and drain into a suitable clean container, you should be able to reuse the fluid if you want to as well. When the pan comes down after draining there's usually about 1L left in the pan. Solenoid replacement is fairly easy, remove retainer, remove solenoid. The filter might be in the way, it's a friction fit into its bore, sometimes it will almost fall out once the pan is off. If you do decide to replace the filter, your parts department might tell you there's two designs, I constantly have that problem with my one partsmen at work, I always go to get the filter he has picked for me and have to tell him "go get the 'other one' "