Is there a manual available for the Vanguard VT-726 tripod? I received it used from a relative but with no manual.

Do you really need a manual for a tripod ? Easy to use - just move the legs to their widest extent, to ensure stability, mount camera on top, attach remote release to camera, aim camera at subject and shoot.
You can download a manual for almost any equipment by Googling the make and model followed by the word Manual, then follow the appropriate link(s).
HTH

Check here: http://www.tripodquickrelease.com/Vanguard_Quick_Releases.htm
They have a very wide selection of quick release plates available.

That's more than I got from Vanguard, they just said they didn't have the part and offered a small discount on a new one, oh yeah so when it breaks again I get the same answer, no way Vanguard

Try www.TripodQuickRelease.com for that part. There is listed the widest selection of quick releases and support more brands than any other web site I've seen.

The part you are looking for is the Vanguard QS-10.

Get it via mail order here:
http://shop.thefotogeeks.com/vanguardvt-840quickreleaseplate.aspx

or ebay:
http://cgi.ebay.com/Vanguard-QS-10-Quick-Release-Plates-/170479531839e

http://www.ebay.com/itm/Vanguard-QS-14-Quick-Release-Plate-NEW-/180693671128

http://shop.thefotogeeks.com/vanguardquickreleaseplateqs-14.aspx

Call Vanguard. They're sending me the lower latch and a foot free.

Inside the flat that accepts the quick shoe you should see "QS- 03". This is the part number of the shoe you need.

I'm not paying for that information.

Think you'll find its a QS29 adaptor which is used on other models. At least the one on mine is labelled QS29 and the pictures look the same. They seem to be available.