The DVD sets are not subtitled and they are HELLA expensive. They have been released in two different versions. The first one consists of six volumes and each volume is 12000yen, so it's 72000yen in total (about $650). The second one consists of two box sets, the first one costs 42000yen and the second one 36000yen, in total 78000yen (about $710). I don't know whether these feature different content though but I guess both at least contain all episodes of the drama. You can buy both versions at CDJapan and the box sets at yesasia.
As for learning Japanese with them, please consider that it's a history drama and therefore the Japanese spoken there differs from what is commonly used nowadays, so it might not be uberly useful (just my two cents, ne, please don't be offended ^^).