I used the PLE for ages before I got my copy of maya, needed to save up, you can enable mental ray if you go to the plug in manager, think its limited to something like 512 x 512 pixels in the PLE though.

You can cheange the resolution of your images into whatever you want (but agian I think its limited to 1024 in the PLE) in the render globals, have a look in there, I think the default value it 640 x 480.

If you render an animation the watermark moves slightly from frame to frame to stop you removing it with filters, again keeping it legal. You get used to it in the end to be honest, and well its free!!

If I was you I would look into getting used to the software render, you can get some really great results with it (have a look at the Maya rendering book, some great examples of how powerful it is in there) by applying reflection maps, raytracing etc.

Looking forward to seeing your porgress.

Cheers