As with any wiki, there is going to be an abundant amount of editors and contributors. You should never consider an entry complete no matter how complete it appears. A new editor could come along and provide far greater insight to a topic, enhancing its content.
The more information on here, the better the site will be. Whenever adding articles or editing them please show a verifiable resource and cite your sources. Unreliable information may be challenged in the page discussion or simply removed. Lack of information is way better than having the wrong information, especially when it comes to your vehicle.
Remember, no one owns the articles on Wikituneup. You do not need to ask anyone, especially the original author, if you can make changes to a particular article. If there is a problem that you can see, just fix it!
Whenever you make a change, whether its minor or major, try to use good practice and leave a note in the edit summary before saving your changes. This is a must if the change you make is going to be controversial. If the same is not sufficient in the summary to explain yourself, just leave a note in the page discussion.
A good tip to follow when it comes to major article changes, is to talk on the discussion page first before actually making the change on the live article. Also remember that if you wish not to fill up the disussion page for an article, you can create a draft of your proposed changes in your own userspace (i.e. User:Example/Testpage) and link it to the article discussion page.