Will I have to convert a Video that was taken on a HD, 12MP Camcorder, before I put it on YouTube?

your dad is wrong, because the youtube viewer can select a lower resolution to view the hd video by themselves, so you can directly upload your hd video on Youtube, but if failed, you should note, youtube only supports some special profile or format hd videos well, so you'd better use a right software to convert your hd videos to right profile and format youtube hd videos, then upload onto youtube quickly, like I usually use Youtube Movie Maker, it can auto convert any format videos to right profile and format then upload onto youtube quickly, just run it, and select upload video, add your hd video into the list, then press SETTING button to select a HD profile as target profile, at last press Convert&Upload button, you will get a right HD video on youtube, and you also can use it to compress your HD video to smaller file size to speed up the upload process, etc, you can download it from makeyoutubevideo.com, hope it can help you.

Depends what format it is. To see supported formats: http://support.google.com/youtube/bin/answer.py?hl=en&answer=55744 As long as people viewing have Flash player or a modern HTML5 browser, they should be able to view it. The "quality" of the video won't have anything to do with accessibility. If it seems to take too long to upload, you may want to reduce the size of the file by decreasing quality.

no, when you upload a video that is done automatically by youtube staff.