Cue disproportionate wall of text:
Getting credits is pretty easy. You get paid by Cerberus after every mission, and you can pick up extra by hacking safes and rifling corpses' pockets and such. Resources you can pick up on missions, but to get a lot you need to survey. It's not hard, but I ended up having a ton or palladium and iridium and frantically scrounging for platinum. On the other hand, you get large amounts of bonus minerals if you imported a ME1 save. Not sure if you automatically get lots, or it depends on how much you surveyed in ME1. My problem was that I used a huge chunk of my platinum on a med bay upgrade I didn't actually need, plus the fact that lots of upgrades need platinum.
You do have to pay for fuel and probes, but not very much. I never ran out of money for them. But you do need to make sure you don't run out of fuel-- if you do, it'll emergency jump to the nearest fuel depot, at the cost of the minerals you've painstakingly acquired. Fortunately, you only actually use fuel flying between systems. None is used in-system or in relay jumps.
I, personally, loathe the surveying. You zoom in on the planet, hit scan, then you hold down the left trigger to scan for minerals. The controller vibrates and a little line graph spikes to show that there is something, how much, and what. Deploy probes with right trigger to collect minerals. There are so many minerals on most planets that it'll take more than 30 probes (default capacity) to get a rock down to "depleted" from, say "moderate" resources. You can land on planets, but only those that actually have something. When you go to them, it'll say "Anomaly Detected" and when you scan it'll show a white arrow and you'll hear a garbled transmission of some kind. When you're on top of it, you'll see a white dot, hear the whole transmission, and be able to fire a probe, after which you can land.