Cal-
How large are your pieces of wood that you need to cut? dimensions (length x width)
All top manufacturers should come with installation details and free training(either onsite or at the factory).
A 50 watt should be able to cut 15mm no problem.... but very very slow.
Regarding 3D sofware..I am not sure about additional software costs for other manufacturers but ours comes at no extra charge and is part of the standard software that comes with each system.
The trick is being able to create the grayscale art work that will look good. There are people that create the artwork for a decent price.
www.gantryco.com is one of the best out there.
The 3D little boy fishing you saw can take anywhere from 10 - 20 minutes depending on the DPI and laser wattage that you choose. Of course less DPI results in faster overall time but not as sharp image and less depth. The larger the laser the faster you can engrave as well.
Off the top of my head a 150 watt laser at 600 DPI will 3D engrave that piece at 15"/ sec and a 400 watt at 50"/sec.
Lasers are very safe as long as you wear laser safety glasses and read through the safety manual.
Hope this information helps.