The storage chest is in an alcove in the wall by the bed, and is different than the locked chest that you need the key for. My post above was meant to be two answers to your two questions, not two related paragraphs, which admittedly isn't an entirely unreasonable interpretation...
If you are fixing a spelling mistake or changing the wording of something, etc, then it doesn't really matter how long after the post was made that you edit. If you are adding new content, then anyone who had already read the original post may not realize anything was added unless someone else replies or they check the topic again for some reason (or you stated that you were going to check something and edit later). I'd post a new reply if you want to add something half an hour or an hour later, and want to maximize the number of people who see it. Alternately, if you edit late and don't get a response in the next day, or whatever, you can probably assume no posters who knew the answer saw the edit, and post a new reply. Or edit and reply saying you've edited your original post (ie changing screenshot links, adding info to a tutorial, etc).
