I wouldn't personally recommend spending the money for Yahoo directory submission. Although it's probably the best directory and one of the only ones to carry weight it'll be hard to make a return on investment even from any SEO benefits if any.
Instead I'd recommend focusing on your website in the following areas:
- call-to-actions - make sure your website's focus/objective is clear to the visitor whether that's directing visitors to contact you or order a service it needs to be clear and easy to do.
- Your content should be well written and targeted to achieve your goal which I would imagine is local traffic.
- On-page SEO - Make sure all of your pages follow the best SEO techniques to ensure the best chance of good traffic from search engines.
- Once the above is done you can move on to off-page SEO which is basically building links but in ways where you benefit from traffic also such as on related forums.
- Then you could invest that $300 in targeted advertising such as banner ads on websites from your local area that are specific to your niche
Hope I helped.