Looking after it
Wood was alive once and hasn't entirely got over it. Treated reasonably, everything here will outlast you.
The one rule
Never put any of it in the dishwasher. Not the boards, not the bowls, not the coasters. A dishwasher combines prolonged soaking with high heat, which is precisely the combination that splits wood along the glue lines. One cycle can destroy a board that would otherwise have lasted forty years. There is no way back from it.
Boards and bowls
Wash by hand in warm water with a little washing-up liquid, straight after use rather than leaving them to soak. Rinse and dry with a cloth, then stand them on edge so air gets to both faces. A board left flat on a wet worktop will cup.
Re-oil when the surface starts looking dry and pale rather than warm, which is usually every month or two at first and then a couple of times a year. Any food-safe hardwax oil or plain food-grade mineral oil will do. Wipe it on generously, leave it twenty minutes, wipe the excess off. That's the whole job.
If a board picks up a smell from onion or garlic, half a lemon and a scatter of coarse salt scrubbed over the surface deals with it.
Furniture
Dust with a dry or barely damp cloth. Re-oil a table top once a year, or whenever water stops beading and starts sitting flat on the surface. That's the finish telling you it's thinning. Same method as the boards.
Keep solid timber out of direct sunlight where you can, and away from a radiator that's on all winter. Both will dry it out unevenly and can cause movement. Wood expands and contracts with humidity through the year; a small seasonal gap opening and closing at a joint is normal and not a fault.
Pens
Almost nothing required. Keep them out of a hot car, don't leave them soaking in anything, and if the finish dulls after a few years a rub with a little wax brings it straight back. Refills are standard Parker-style and available anywhere.
Marks, dents and time
Let them. A board that's been used looks better than one that hasn't. Deeper knife marks on an end-grain board sand out with 240 grit and a re-oil if they bother you, though most people stop bothering after the first year.
If something goes wrong
If a piece splits, a joint opens or something turns up damaged, tell me. I made it and I've still got the offcuts, so I'd rather repair it than have you throw it out. That holds whether it's a fortnight old or five years.