The "official" way is to disassemble the engine (you have to remove the crankshaft) to install an endless chain, that might explain 14 hours. Just re/reing the engine in a 750 could take me several hours though, and the frame doesn't allow valvetrain work with the engine in.
If you use a master link (riveted, NOT clipped) chain you still have to pull the motor but don't have to take the motor completely apart. Unless you are doing other work requiring getting into the bottom end I would strongly recommend the master link chain!
See if they will do the job on straight time (ie how long it actually takes) rather than book time (they likely got the 14 hours from a job time book). I would guess you should be in the 5 hour range with decent mechanics and the right tools. Someone who has worked with a lot of CB750s could do it in quite a bit less time if really motivated.
Instructions:
You need a new master link chain, a rivet master link for it, and a clip master link for it. Plus a dremel tool and chain breaker/riveter for the chain size.
Remove engine.
loosen cam chain adjuster. (or remove it, you should check the roller and probably replace it anyway).
Remove valvegear cover.
Loosen all 8 tappet screws fully.
Tie a wire/string to the camchain ahead and behind the sprocket. This lets you retrieve it if you drop it... remove the front one after you get your new chain attached with the clip link.
Cut through the side plates of the chain with the dremel tool behind the sprocket (intake side) then use the chain breaker on the "front" (exhaust side) end of the chain to push the pin out so you can use a clip master link to attach one end of your new chain to the "front" end of the existing chain. Do what you can to keep the chain cutting filings and bits of chain from falling into the engine. Don't turn the crank without the chain on the sprocket, and keep the sprocket teeth in same chain links (ie mark a tooth and link so they go back together with the cam timed properly).
Slowly turn the engine over while holding the chain FIRMLY on the sprocket so it doesn't jump teeth... pull the new chain through until the clip link is at the top of the sprocket. Remove clip link. Install and rivet the rivet link.
Check cam timing. Tighten tensioner. Set tappet clearances. Reinstall valvegear cover. Reinstall engine.
There are other approaches, this is how I've done it. I don't know if the valves will hit the pistons with the tappet screws backed out - I didn't try turning the crank separate from the cam... if you're super careful you don't need to unscrew the tappets I suppose, and not have to reset the clearances... I'm a bit nervous though. If you do pull the cam out you have a LOT more room to attack the top loop of camchain and can split it with the breaker (there's no way my breaker would fit in behind the cam sprocket).
