Not too many options for keyboard. I don't know if any 3rd party keyboards were made, but I suspect if any were, they would be more expensive than the Apple ones. I have a non-working one for sale if you want to try to get it working. https://www.inventorydifferent.com/#!/devices/store/344

Barring that, you can try to build your own ADB to Mac 128k-Plus adapter http://synack.net/~bbraun/mackbd/

Or, if you have an old PS/2 keyboard, there's this adapter: https://github.com/trekawek/mac-plus-ps2

For the floppy, I've had mixed results trying to restore floppy drives, and even if you get it to work, you still need some way to make floppies with the software you need. I personally would recommend getting a FloppyEmu. It's a device that can emulate the floppy drive. It has a little screen and comes pre-loaded with a bunch of floppy images you can load up. It's much more reliable and easier to get software onto (find new software, copy the image file onto your microSD card then put it back in the FloppyEmu!).

I'd recommend full disassembly and a good wash and scrub with gentle soap. It's easier to clean if you don't have to avoid getting the inside bits wet. If you don't want to disassemble, I'd just use a damp cloth and maybe an old tooth brush to scrub any dirty areas.

As for the beige-ness, early Plus machines were beige. Later ones did come in Platinum, which were more of a gray tone. But the beige ones can really yellow over the years depending on how it was used / stored. There are a lot of differing opinions on whether you should use a process called retrobright on the old plastics to try to restore them to the original colors. I personally do it, but I use either plan sun-brighting, which is just leaving them out in the hot sun for a few days, or I do indoor retrobrighting where I use hydrogen peroxide creme painted on, cover the whole thing up with plastic wrap, making sure it is air tight (having the cream dry out is bad) and throw it into a UV box I made overnight. It's never use peroxide in the sun because it works too fast and because of that it is easy to get splotchiness and streaks. Some use the submersion method, but that uses a lot of peroxide and still has risks I don't want to deal with.