STALKER: SoC is extremely confusing. It doesn't give you that much an indication of where to go and what to do.
I have gotten to Yantar where I got that pretty nice bio suit from those two scientists, and my only Main quest objective is to find out more or where Ghost is.
Am I on the right track? This game is good but damn confusing.

It has been a while since I got past Garbage in STALKER (AMK with Arsenal is just amazing), but I think you are good if you just keep following map markers and the like.

Yantar... Okay, so did you already go inside the zombie-infested lab facility in near Lake Yantar? You're supposed to go in there and disable the brain-scorching radiation machine inside, with the helmet the scientists gave you as protection from its psychic effects. Ghost's corpse will be inside.
If you've already been in there, but didn't find Ghost, you need to go back in again. Once you've disabled the first brain scorcher and found Ghost's body, your next step is to disable the BIG brain scorcher up in Red Forest. Once that's open, the road to Pripyat and Chernobyl will open. And once you get to Chernobyl... Well, that's when you get to the "multiple endings" part of the game, and I won't spoil that for you.

Thanks to both of you. That is very helpful.
So I suppose it's quite a short Main quest then. Might as well do some side quests.