Hi & welcome to the forum.
Good luck with the venture, not easy in the current climate but probably the best time to go for it
I don't know much about product photography but this is my opinion...
You say that you've been using a point and shoot, in what way do you feel that, that isn't good enough?
Is the jewellery being modelled or are you using placement (stands etc). Either way tripod would be a must but the type may differ and remote shutter control to reduce camera shake.
The main thing to consider for this type of photography is lighting. To avoid direct reflections, the flash would need to be heavily diffused and preferably taken away from the camera so either a flash gun with off-camera cable or a mini studio setup with decent lighting would have to be considered.
Other things to consider are .. once the pictures are on the pc, then they will probably need retouching to promote your professionalism and unless you use one of the free packages, the software can be expensive and the learning curve very steep.
To get the best from a DSLR, especially under these conditions is also going to be a steep learning curve and very time consuming.
The camera itself is not the major factor in getting good shots, it's more down to the quality of lens used and other equipment used like the lighting, to aid the photographer to get the desired images.
If you are fully prepared for the whole package (cost, time & learning) you will be taking on and still want to go for it, then good on you

If this puts you off in any way, then it may be cheaper and you should get better results from day one, if you hired a photographer to come in and do it.
Hope this helps