A few tips about the Firefly renderer:

1. NEVER use the presets in the Render Options dialog. Switch to manual, and set your options there.
2. In the manual options you can uncheck "cast shadows"
3. Still in the manual options, you can reduce the shading rate to 0.2-0.5 - this will give you better looking textures with more detail.
4. Set the maximum texture size to an appropriate value. Guestimate how many pixels high the texture will be on the largest object on screen, and round up, preferably to a power of 2.
5. Use smooth polygons if you make closeups
6. Check 'Use displacement maps'. Many P6 materials have displacement mapping that will increase the quality of your render
7. Uncheck texture filtering. It gobbles up memory.

Another way of making the shadows disappear is making the GROUND object invisible in its Object Properties dialog. 

You can get the correct render sizes in the Render Dimensions dialog. Set the dimensions, choose Inches as unit, and set the DPI to 300. Render to a new window must be enabled. A word of warning though: 8.5"x14" will result in a render of 2550x4200 pixels; this is rather large and will take a LONG time to render. And you may run out of memory.

If it renders out OK, just save as .psd and you can do in Photoshop whatever you want. The .psd contains an alpha channel, so it's easy to get rid of the default grey background.

Do not underestimate the raw power of Poser 6. Check UweMattern and richardson in the galleries - that'll give you a good idea of what Poser 6 is capable of without postwork.
Poser 6 is also quite complex - it comes with the power. It'l take some time to unleash its full potential.

This is not a purely technical question. You're better off posting questions like these in the main Poser forum - it's a lot busier than here.

Happy rendering!

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