I'll second the cleaning and lubrication of the 400k drive. The grease that Sony used on those drives back in the day is no good anymore and it'll keep the mechanism from working properly or at all. The gear Ray linked is for an 800k drive, the Sony 400k drives are all metal linkages so there's no plastic gears to strip out there. I'll again second Ray and say you want to pick up a Floppy Emu, but add you'll want one anyway no matter what you want to do for the physical floppy drive. It's just /so/ much easier to dump your collection of disk images onto a Floppy Emu and boot those than have to worry about getting a compatible Mac and fussing with Disk Copy, or bootstrapping BLU over serial and writing disk images over serial.
For hard drives, an X/ProFile or a Cameo is the way to go. If I didn't already have an X/ProFile I'd probably go with the Cameo myself since Tom has been doing some amazing work with the Cameo that makes it a lot more user-friendly than the X/ProFile is. You will have to get a run of Cameo boards made if you want to go down that route, but I know PCBway can do full assembly of the boards for you for an extra charge. If you do go down the Cameo route, you will have to get a Widget to DB-25 adapter from VintageMicros, or find a dual parallel card.
For my keyboard, I used TexElec's premade foil/foam discs and I've had absolutely no issues since:
https://texelec.com/product/foam-capacitive-pads-keytronic/ They're fiddly to install as you have to make sure that the plastic disc that makes up the sandwich gets properly clipped into some very tiny plastic clips, and you want to make sure you either use latex/nitrile gloves or tweezers to install the discs since finger oils could keep the keyboard from working properly.
ETA: If you do end up replacing the drive with an 800k drive, you'll need a new set of drive standoffs to get the 800k drive to align properly with the faceplate opening. You will also have to replace the disk I/O ROM with the Sun Remarketing 800k ROM as the original disk ROM doesn't understand 800k drives at all. The ROM can be found on BitSavers if you have the ability to burn it yourself. Lisa Office System doesn't understand 800k disks by default; you'll still only be able to use 400k disks unless you also load the 800k driver:
https://macintoshgarden.org/apps/lisa-office-system-800k-driver