You could always make aircraft for CFS2. I need a few more WWI AC's
or
You could find someone to team up with that could convert the models for you.
I second hairyspins comment on software choices and cost. I use Gmax and Paintshot pro X3 on my XP comp. Gmax and Paintshop pro X5 on my Win7. I've used PSP since psp 8. I like it better then photoshop. But I use them for more then just the flight sims. So I can justify the cost.
I would start small. learn the software. Make a few little models. Buildings are a great start. learn how to texture the models. learn about LODs and animations. lighting effects. take it slow to start. if you jump into something too big you will burnout and lose interest really fast.
Ask questions and build a group of mentors/advisors. We have some of the best around right here. The rest is having fun. Think of it as your own modeling kit. Just it doesn't require the physical materials to make a model.
Hope to see your work here in the near future.