Brick and mortar is laid by hand. The repair process is a manual one too. For both problems, your best bet is to hire a pro.
Sorry to say that but maybe you can 'help' the pro (as a 2nd hand) to cut your costs. Have him price the job himself and ask him if he will have 2 people do the job. After you get your 2 or 3 bids, ask if you can have a 2nd bid with YOU as the helper. Tell him he's gonna have to show you 'how to tuckpoint', and so on. At worst, ask him if there's any prep work you can do to save some $$$.
Yes, I would believe that NOT fixing this will cause more problems. (Obviously, I can't see it from here so it's just a gut feeling for a 1900's house.) Have a few pros give estimates anyways. Their rates may surprise you in a 'positive way'. And eventually ask about helping or doing prep work to save some $$$. My best to ya and hope this helps.
PS: Even if you 'fix' all this, your water issues may not go away. Here's some related reading. Read through this Follow-up and see if there's anything you can do NOW to help alleviate your water problem. It's Basement Water.