A word of warning: It's certainly possible, but it will take you years. Don't let that stop you though. Hasn't stopped me (though I'm waiting untill I can code well first).
I've never used poser 6, but you'll need some sort of 3D modeller and an animator. You'll also need some music software, and some 2D paint-editing software. In DB discussion, there's a sticky with a list of software and where to get them.
Quote: "Where can I learn to make a full-length RPG on DarkBASIC Professional"
There are no tutorials for this for obvious reasons. I'm going to assume you're new to DB, so I'll suggest two ways of starting out.
The way I started out:
Make small programs, and experiment with the commands that are relevent to your project. For instance, make an RPG menu with a party switch system. Do it several times in different ways. So far I've done two menu systems, and three battle systems in the last couple of months. Each time you do it, you'll think of a faster, better way, and add more commands. The amount of code it takes will decrease too.
The plus side of this, is that if you're impatient (like me), then you'll feel that you are always making progress towards that final game, and therefore stay interested in what you're doing.
The downside is that it takes longer to learn the language, and some commands and techniques will never even be touched upon.
The recommended way of starting out.
Start off with simple arcade games in 2D. Pong, space invaders and breakout will get you using basic commands and maths early on. From here, you can advance to harder stuff like a 3D pong game or something.
The plus side here is that you will get a firm basic knowledge of the language, and you'll be able to increase the difficulty gradually.
The downside is that you may think that pong is boring compared to FFLVI.
Whatever, either way, you won't be ready for an RPG for at least a year. Make a design document in the meantime. That way, when you're ready to make the game, you know what to do and how. The design part is both the most geeky thing you'll ever do, and really, really fun.