As a quick workaround (whilst you procrastinate and put off learning UV unwrapping because it doesn't seem that important yet...) I sometimes do the following:
1. Make sure your object is an editable poly, or apply an edit poly modifier
2. Select the sub-object element for the part you want to edit
3. Rotate around the axis relevant to the wood grain you need to change
4. Leave sub-object mode and rotate at object level back to the original position
This will effectively alter the objects UVW coordinates, I use this process a lot when I have a triplanar wood material instanced across multiple objects, I find it quicker than unwrapping everything.