Yes, you can do it! Have a look up in the right corner of your screen, these are not complex machines in a modern sense. The engineering is sound and logical (usually) and parts are available (mostly) and there's always tons of know-how to be had for free here from the membership. first read the FAQ, then just pick a spot in the SOHC/4 bikes forum and read, read, read, search search, search, and then ask every question that remains. Post your progress in the Project Shop forum and take pictures, notes and measurements of everything.
My first suggestion is to spray evert nut and bolt on the bike with penetrating oil asap, then every day until you've emptied a can or two. PB Blaster is the weapon of choice, but even the K/wal-mart brand will help free things up, don't try to crack loose any nuts or bolts without spraying them down, they may be stuck and snap.
If the engine turns, you're in luck. If not spray some penetrating oil in through the sparkplug holes then put the plugh back in (they don't have to be tight) and go read threads on freeing a stuck motor.
The plugs require a narrow thin-walled socket to fit correctly, the stock tool is still available from your honda dealer, search for more info.
For a great source of part numbers, screw and bolt lengths, and a whole lot of other info... become familliar with
http://www.servicehonda.com/test/index.htmMy 750K3 had a build date of 10/72 so I've got an idea what you're into, enjoy!