Males should wash males and females should wash females. The ghusl is done (or supervised) by someone who knows about the process and rulings of washing the deceased.
If a person dies without saying the shahädah, it does not mean they die as a non-Muslim. As long as a person dies with the shahādah in their heart, we always hope that Allah will grant them Jannah.
The purpose of visiting the graveyard should be to reflect upon one's life and actions and to think deeply about the preparations a person has made for death
Three things follow the deceased [to their grave]. Two [of them] return, and one will remain with them. Their family, wealth and actions will follow them; their family and wealth will return, and their actions will remain
When a human dies, their deeds cease [to be recorded and thus cannot benefit them] apart from three: [leaving behind] a continuous charity, knowledge from which benefit is gained, or a righteous child who makes du'a' for them