Are you trying to modernize it or going for the mid century look? There are very different answers to your questions depending on the outcome you want.

If you are trying to modernize it then you need to remove the bulkhead over the "L" along with the scallop over the window. Adding crown molding at the ceiling over the cabinets will update the look too. Replacing the light fixtures and the knobs as you noted. The floor you have many choices but installing a laminate yourselves saves some money for a great countertop. Don't feel you have to go granite there are so many alternatives and laminate and marmoleum countertops have come a long long way. Look into the new edging techniques for the counter. As far as colors you would want to select something you like. Black is a bear to keep dust and speck free subtle patterns are always easier. I suggest you go shopping and see what hits you for a backsplash then select a counter that coordinates then worry about the floor. Backsplashes are easy to change down the line and you can go a bit more creative with them.

If you are trying to retain the mid-century modern look you would want to work around hard colors such as deep red, golds, oranges, green, very yellow, aqua or a hard pink. In that case I would do a marmoleum floor with a design. Pick a strong color for the counters and stay with the 4 x 4 tile backsplash.

If you just purchased the home and have no intention of selling it right away do what you want and have fun with it. Some images to ponder in Mid century modern.

I would like to modernize it. I love a black countertop.. Going to put laminate in. Not sure about the floor. I like a bold backsplash. Definitely changing the lights and also the hardware on cabinets. Old hardware left marks on cabinets. Do you know how I can get rid of that?

Dirt marks or indentations? For dirt marks get some Barkeepers Friend and a green Scotchbrite. If that does not pull the dirt off then the wood has been stained deeper. The only thing to try at that point is to make a poultice with bleach covering it in plasticwrap and letting it sit overnight. Most likely the finish will be compromised in that area from grease and your cleaning. You can return the sheen with a bit of varnish or shellac - polyurethane may not stick correctly. Indentations will require some wood putty sanding and staining with an artists brush.

Do consider adding crown molding to the top of the cabinets it will lengthen the look of the older style cabinetry. also removing the bulkhead will open the room. I have attached a fast mock-up of those changes.

If you are going with a black counter top you will want flooring that compliments the maple. If you go with a compliment to the black counter top you will find you have created a very dark space. Very modern...but very dark. With cork flooring ('cause that is what I know) the strong yellows in the maple work incredibly well with the strong yellows in cork. Even though cork is an oak, its colouring has great complimentary range with maple.

Black countertop, Ceasarstone or some type of Quartz would look wonderful....Long stainless steel pulls for the hardware on the cabinets would give the kitchen a fresh, contemporary look.
Good Luck....

How about marble subway tiles, and a tile stone floor that looks like marble. You can purchase the tiles at "Lowe's " and they look great and will give you a contemporary look with a touch of traditional.

OK, I'm back. Here are some images that may inspire you:

Marci4 is dead on with her images. MCM is not a jetson's look like the photos posted by lucidos. The kitchen has great bones and is most likely very well organized and is pretty much indestructible. If the kitchen is untouched, I'm assuming the rest of the house is as well. You have an investment property much the same as the love of craftsman, Victorian, etc. Be very careful how you proceed.

Also your floor looks like it might be terrazzo. If it is, you definitely need to clean it up and keep it.

Four years later...I'm wondering what you ended up doing. Please post updated photos!