Yes, call MS. Just keep your requests simple. The more you request, the harder it is for them to guess what is most important to you, and therefore more likely that you'll be disappointed.
Here's a link to a map of OKW:
http://www.wdwinfo.com/resortmaps/okwmap.htm
Just be aware that you will NOT be able to get Hospitality House area buildings. Those are a separate booking category reserved for DVC members only. I believe the HH category is
Bldgs 11-14 and 23-26. If that is not accurate, someone please correct.
When we visited last December, we asked for and got Bldg 45 with a perfect view of the canal.
Good luck and enjoy OKW!