If you do not know how to edit, save yourself the time and get someone who can. Don't trust your creation with someone that can ruin it.
First of all, no one's first draft is the best. If that's the case, you're saying the more you write, the worse you get. That's the complete opposite of how writing works. As an editor, I've seen some damn good first drafts, and even those have cringe worthy typos, errors, and general problems. A first draft plays a key role in the writing process though. The worst thing you can do is not give your manuscript enough effort to mature it.
Secondly, there's no difference between refusing to edit your work and editing it incorrectly, whether by you or someone else. I often see authors over correct, therefore, convoluting an amazing concept. I've also seen authors make the wrong corrections. Dialogue is very easy to mess up. I've seen people take correctly written dialogue and butcher it with punctuation. I've also had friends give me edits that completely change the style of my work while others have had me scrap perfectly good scenes altogether because they couldn't relate to it.
Besides knowing HOW to write, a good editor should also be able to take YOUR style and what you're already bringing to the table and enhance it while working on your weaknesses. This is why it's important to have some sort of rapport with your editor. I've been fortunate to build a relationship with my authors and I feel a big part of that reflects in the work. I can only imagine if you're trying to complete a project and you frequently don't see eye to eye with someone about something you created, it's bound to get frustrating and that may prevent the best work from happening.
When selecting an editor, keep in mind that your writing is extremely intimate and find an editor that you mesh well with. Through Vital Narrative's consulting services, we have developed a great process that encompasses all levels of editing. With this process that we implement, it allows us to offer a thorough, helpful, educational, and meaningful experience. On top of bound copies that the edits are in (and extras for yourself), we hold a private meeting to discuss your project so you know your next steps and what you're doing. Essentially though, when selecting an editor keep in mind that as a creative outlet, writing can be extremely intimate so find an editor that you mesh well with.