It's not having the blog, per se, as much as it is the fresh content being added regularly that helps you out.
It's definitely a good idea to have your own blog. It's best to use wordpress.org not .com You can set it up really easily through GoDaddy, because they have a really good interface to upload a wordrpess blog. You may think about buying an older domain name, because you'll rank much faster in Google with all other things considered. Dave
all depands on what your aim is. Blog can be used as direct as well as for support kind of a thing for your particular business. Also blog can be used as personal also, where you can share about yourself..
A blog can certainly help with SEO but you really need a solid strategy of how to create content, schedule it's release, decide which format works best for you, etc. Get your ducks in a row before you launch your blog so you can run it - rather than have it run you.