Jacqui,
It all sounds feasible to me, and I think the Tormach is a good choice. Their tooling system looks very good, and repeatable tool holders is really the key to efficient machining. I always keep an edge finder and a dial indicator mounted in tool holders permanently, because you always need them. Cam programs are usually described as 2D, 2-1/2D, 3D, 4D, and 5D. 2D is a program that can produce a gcode tool path using 2 axis, typically the X &Y. 2-1/2D adds the ability to also control the Z for things like drilling and pocketing, but not simultaneous with the other two axis motions. 3D gives you contouring of organic shapes ( the sexy curves stuff). 4D usually adds a 4th rotary axis to mill on the sides of parts that you rotate, or to simply re-position the part to do other sides without re-fixturing. 5D usually involves being able to also tilt the spindle in some direction. Cost and the skill required by the operator goes up quickly!
I find that before I try programming a part there are two issues that need to be considered first. What tools do I have available? Sometimes you can do a part with simple tools, and sometimes you get a huge benefit from having special tools that may seem costly at first. For instance, a shaped tool that produces the groove that the lens fits into may warrant a special tool. I used to have an endmill with a reduced section part way up the tool. I used it to circle interpolate a round nub with an undercut to mount vacuum cups. A local tool sharpening service modified an end mill for me.
Holding parts is often a huge issue. If you are clamping a part down with clamps that stick up you may have to program interrupted cuts to go around the clamps, and Cam programs that can easily do that are much more complex and expensive. Sometimes you write a program in multiple parts, with a pause to move the clamps. I've even used double face tape on plastic parts. If you are doing multiples you may want a Cam program that can easily nest multiple parts on a single sheet. Doing this manually can be very time consuming.
Since you are only trying to do one type of part, and not job shopping all kinds of parts, that should make your choice easier. I would take the time to figure out the tooling and holding questions so you can factor that into your Cam requirements. If you are already using a 3D cad program to do your design work, things will be much easier. If not you have a double learning curve. Cam programs need some sort of model to work with. I once worked at a place where I programmed machining centers to machine castings made to 50 year old paper drawings. I programmed everthing manually because making a 3D model of these complex casting would take days. They replaced me when a left with a guy dragging along his own computer and MasterCam. He didn't last long!
If you are not using a 3D modeling program I suggest you look at Rhino3D. Lots of artistic people using it, and the user forum is a fantastic resource. There are also several Cam programs that run from within Rhino. MadCam and RhinoCam, are two of them.
Hope this helps,
Gary H. Lucas