So I have two ferrets both a year old, I am currently feeding marshall kibble diet.. They seem to be healthy but I don't want problems to arise in the future. I have some questions so can anyone help? I want to do a half kibble and half raw meat diet (kibble during the day, meat at night)
How should I switch them to meat?
What kinds of meats to start with?
Can I buy the meat from a grocery store? 
If anyone can answer these questions and explain how to switch them over I would very much appreciate it!!:)

"How should I switch them to meat?"- To be honest, there are many methods to try. Some ferrets are super picky and some will eat whatever you give them. Last year I switched my 3 one year olds to a raw diet from Marshall's Premium. What I did first was buy some commercial raw product, Nature's Variety Instinct Raw Chicken Bites to be specific. I offered it to them cold and they weren't interested. I warmed a piece up and my female took it and stashed it. I was happy she took it but didn't want her stashing meat everywhere so I added hot water and made a raw soup. My female dove right in to the soup and my boys followed suit when they saw her enjoying it. Once I was confident that they liked it and would eat enough I took away the kibble and they have been on raw ever since. I chose to stick with commercial raw instead of moving on to RawMeatyBone or BARF style raw feeding. I have offered whole chicken wings and chunks of various meats but they tend to get played with and stashed unless the meat is a chunky soup type of consistency. If yours are pickier than mine there are other methods that I know of; you can mix their kibble with the raw you want to switch them to and make a soup out of that so they get used to the taste. You can also crush the Marshall's into a powder and use that to coat the raw meat so that it smells the same. Some people use Ferretone or other treats drizzled onto the meat to entice them to try it. Basically any tricks you can think of to get them over that fear of the unknown. Usually smaller pieces or soups are more easily accepted than big chunks or whole chicken wings.

"What kinds of meats to start with?"- Chicken seems to be a very well accepted flavor for ferrets, and that is what mine started with. I figured since their kibble was mainly chicken based it would be the best to start with. From chicken we moved on to duck, beef and lamb. The duck and lamb have very strong smells compared to the chicken but once they tried them ( i mixed them into their chicken soup) they liked them both. None of my 3 liked beef at first but once they got used to it they started loving it. In total mine have had chicken, beef, duck, lamb, turkey, pork, goose, bison, rabbit, salmon, and venison. If I had to guess based on how much they eat and their reaction to it; chicken, beef, duck, and lamb are their favorite and they seem to not like rabbit very much.

"Can I buy meat from a grocery store?"- Short answer, of course! Long answer, it will take much more work to prepare and properly balance between muscle meat, organ meat, and the proper amount of raw bone. It will probably take more work to get them to switch to it, as eating a chicken wing is radically different than eating from a bowl of kibble or even a bowl of raw soup with ground bone. It might be a lot messier, like the issue with mine and the stashing of chunks. But you will save money, most likely a LOT of money! And eating something like a bone-in chicken wing is very healthy for their teeth, my main concern with my commercial soup diet (other than the cost) is the health of their teeth. If you go to the Holistic Ferret Forum they have mentors who can not only help you switch your ferrets but also help with a meal plan that is properly balanced. Hope this helps and good luck!

google ferret raw diet. Look for the post by hollistic ferret forum. It has a great recipe to switch them to. I am a strict raw feeder. If you do half raw half kibble be sure to put the kibble out in the morning. Let them eat and then take it away.