Since this is your first short film, your best solution may be to work with what you have right now. When you figure out what, if anything, does not work for you in using that camera, then you can look at upgrading. Perhaps your budget, at this point, would be better spent on camera support and, very importantly, sound.
Regarding 1-chip vs. 3-chip: for small sensors (chips smaller than, say, APS-C), a single chip has a lot of information to cram into a small space. This means that the resolution of the end-product is limited to the capacity of one chip. By splitting the incoming light through a dichroic prism and sending each part (red, green, blue) to its own chip, the workload is spread out and the three signals composited into a single image that has a higher effective resolution. Three chips are always better than one if your camera has 1" sensors or smaller. These days, however, CCD is pretty much obsolete and most cameras use CMOS (some 3-chip CMOS cameras may say "3MOS").
Once you get into larger image sensors, there's enough surface area that collects enough data to create a very detailed image from a single chip. DSLR (both crop sensor and full-frame), Black Magic, Digital Bolex, RED, Alexa... these are all single-chip cameras. Their sensors are large enough that they don't need more than one.
What you may find is your biggest limiting factor right now, at some point, is shooting on a standard-def camera. If you are shooting for Internet distribution, then you need to be able to shoot progressive (24p or 30p). If you can only shoot interlaced, you'll need to deinterlace before publishing to the web, which will cause a reduction in resolution.
Learn with the camera you have. If you can make a good image with limited technology, you'll be in a better place when you have better gear. And if/when you do decide to upgrade, look at HD offerings.
