David - This looks like a great boat! We owned an '82 Sabre 28 for 15 years that we sold 4 years ago... only to buy another Sabre. You'll love this boat. She's rugged and looks to be in great condition. I'd recommend that you work on a lower price though. $24900 is a bit high, but not that bad. Try for $22k.
We had a Westerbeke so I'm not exactly sure what you refer to without a photo. However, in our '84 Sabre 38, there is an engine cutoff "T" handle which is a choke. Our 28 had a knob that was pulled - same idea, but in knob-form. The 28 & 38 have a glow plug. Since it's a "T" handle, I'll wager that one is the cutoff and the other is a compression release as JohnR says.
With this boat, be on the lokout for poorly sealed chainplates and associated rot in the bulkheads below. Also look at the teak handrails on the deck. Sabre didn't seal them the best and there could be some deck delmination. Not a huge issue, but you could get some $$$ off.
you can stick your finger through a bulkhead
Probably bad chainplate sealing - I got $10k off my boat. See the following link for the repair that I ended up doing:
S/V Victoria Head Reconstruction
or the cabin sole near the mast step
This is a common problem with this vintage boat. The mast drain was poor and would rot the floor. I walked away from two other boats until we saw Victoria. The PO had a new cabin sole installed - real teak and holly, not the plywood that Sabre used. Fixed the drainage problem too. Basically, I bought the boat for this stellar floor! Sorry, I don't have any photos on my site. Good luck with your search. If you're in the Annapolis area, I recommend Dan Nardo at Annapolis Yacht Sales.