I'm going to handle the topic of the afterlife first, because I think it's the most important. A lot of people make the argument that if people 'really' believed in the afterlife, they would get themselves killed so they could go there. However, what these people neglect are the great poems and stories written about how much it sucks to go to heaven. The best example I can think of are <PERSON>'s Elves: they all eventually sail to Valinor (which just so happens to be where they go when they die), but even though they know they're going to a better place ,they still really hate to leave Middle Earth. That's the general argument: heaven is nice, but Earth is really good too, and once you leave you won't be coming back. Plus, there's the phrase "you can't take it with you", which in this context takes on a whole new meaning...
As for how people would deal with death, I had an interesting conversation with an old roommate once about his concept of the soul. Basically, for him, if anything of us survives after death, it's nothing like what we appear to everyone else. 72
So, even if our souls survive, we must lose something when we die, and that's still something to be lamented. Like it or not, your body is a big part of who you are, especially in the context of your interactions with others, and your society will most likely understand that.
Add to all that the fact that dying is probably still really scary from an evolutionary standpoint, and I'd imagine most death practices will be very similar. That doesn't mean you're stuck with whatever rituals your personal culture does; our world has many different ways of sending someone off permanently, I'm sure you can find one that fits your needs.
As for gods, again I think things will shake out pretty much the same. To me, your gods sound way more abstract than the bearded guy most Christians think of; however, your world will most certainly anthropomorphize them. The 'cosmic flow' sounds like something scientists won't be able to accurately describe for millenia; until that time, people will make things up, just like they've been doing here. Not only that, but people will attribute to the gods things that they shouldn't: for example, regardless of whether or not the gods can hear them, people will pray, erect statues and churches, and burn cows, because the placebo effect and the joy of working together with a like-minded community will make them think it works.
What I'm trying to say is that not a lot has to change. This is just one of many possible answers, though, so hopefully if it's not what you wanted someone else will explain why leaving dead bodies where they lie would totally happen. 752