Yes, I agree that the soldier picture is well worth the purchase. And yes, the glass can be easily replaced (probably with glass from one of the other not so good cased images of the same size?). And yes, rotate the mat when doing so.
However, I would say that some of the other images are quite nice. There are people who like non-military images. Even with the brown spot of foxing dead center, the child in the white dress is nice. The "can we get this over with" expression is priceless. I have seen images like that get $15 to $25 retail. The Little boy has a darling outfit and should be an easy $25 to $35 retail. The dapper gentleman and the woman in the bonnet is an excellent image. I would say pre-war from the clothing and it appears to actually be a daguerreotype. The image looks mirror-like to me? If it is, an image like that can retail for $45 to $65 fairly easily. So, just in those three I think you are looking at $85 to $125 in retail value. The very spotted old white haired gentleman is a parts piece for the mat and case. The woman with the white collar and bonnet (lower right, behind your dapper couple image) and the man in the dark suit with the white cravat that you are holding in the second image are decent but certainly dime a dozen images. I see them get $10 to $20 sometimes.
I didn't see the other three images too well, but the one damaged woman image in the background of the second image isn't worth anything. But I think you did excellent! You could maybe sell the five I talked about to a dealer for like $75 and you got yourself an great soldier image for $25! Or keep them because they are cool historical images...I do like the dapper couple image. If it is a daguerreotype you have yourself a nice example of early photography.
The Daguerreotype is the first form of photography; introduced in Paris by Louis Daguerre in 1839. So, you may have a nice example of the very first photographic process. The three primary forms of early photography are; the Daguerreotype which is an image on a copper plate coated with silver which gives it a mirror-like look. A little later came the ambrotype which is an image on a glass plate; it is actually a negative image that looks positive against the black background of the case. And later came the cheaper tintype, which is, well, an image on a tin plate.