So, dying... yeah...
#1 Dying is possible, but not very easy.
Hitting 0 hit points does not mean "dead". In general I will follow the rules which have the conditions of "Unconscious/Dying/Stable/Disabled/Dead". Exceptions are possible, but will be rare. (IE. If you have 20 hit points and you take 30 points of damage you will probably have to make a save to prevent dying from the sheer shock of such a massive wound. )
#2 Coming back from the dead is not certain.
It's likely, but it carries risk. The actual spells to do so are cheaper than shown in the Core Rules, but they now carry a chance of failure. That chance of failure can be reduced considerably based on the actions of the party towards their companion.
In short, consider that the soul needs to be "brought back" to the body (That's what the magic does), and it also has to "want" to return.
Let me give two examples.
Party #1 has one of their group fall in combat. They strip his body and leave it sprawled naked and dirty in a manure cart while they trudge back to town. They constantly talk about how foolish their friend was to end up getting himself killed. When they find a high priest to resurrect him they dump the body on the temple floor, tell the priest that they need their friend awake by morning, and head to the local pub for drinks. (Chance of success? Very low)
Party #2 has one of their group fall in combat. They take time and care in cleaning the body up and keeping it clean. They also find a manure cart to haul the body, but the wizard uses prestidigitation to clean it up. They regularly do caring acts like placing trinkets with the body, say to the body about how much they miss their friend, place flowers on it, Etc. When they also find a high level priest they pay him extra and ask that he please take his time. They all stay for the ceremony and take their turns explaining why they want their friend returned to them. (Chance of success? Very High)