Yep, load up before and continue after.
Kombucha is fermented tea (sort of). It's actually a combination of a few different things. You can make your own, but for safety's sake, you can also find it refrigerated at most fancier grocery stores. Wegmans, Trader Joes, Whole Foods, and lots of other ones carry it. Kefir is fermented milk, sort of halfway between milk and yogurt. It's sort of fizzy and contains more probiotics than yogurt (from what I understand). Both are nice because you can just drink them down. Both contain trace amounts of alcohol, however (like 1% for kombucha) so don't go too crazy. Kombucha too can have a pretty high sugar content, so you want to make sure you balance that against the probiotics you're getting. You might want to ask your doc, since while the food sources of probiotics are more bioavailable, it might just be better to take whatever you're taking and not overthink it.
If you like it, you can also munch on fermented vegetables like sauerkraut (just make sure to get the real stuff, not the pasteurized kind).