I agree with the comments above. A-30 is a sold old boat. And, I agree with your approach to assessing the boat. I wouldn't put much if any stake in the last guy's survey.
If you can find a surveyor for a couple hundred bucks, I'd jump at it. They will teach you a ton in 4-6 hours on the boat and possibly save you from ruin (if they find something wrong that you'd miss). Otherwise, read read read (there are a handful of "assessing the aging fiberglass sailboat books). After you get done reading make a checklist -- don't just copy it make one yourself so that you stop and think about each item. Make sure you have all the tools you need (borrow a decent moisture meter).
Questions: who put the engine in? That thing oughta look good with those sort of hours. Otherwise a deisel doesn't usually show up in a cheap A-30. Did the non sailor install it? If so, it could be totally screwed up. What is the "teak restoration" just finish or is veneer peeling off? The first is nothing -- the second might suggest more serious issues. Don't let the "dirty" conceal real problems -- clean while you survey if need be. It is easy for anyone to look into an unfamiliar bilge and miss stuff - way way easier for you and worse if it is dirty.
. All of the above are exercises in determining what you are buying and that it is not screwed up worse that you think you know. But you are going to spend a boatload of money on stuff that the boat doesn't have. You need to compare this boat to one that is better equipped. That is especially true in this market. $5K in boat crap is NOTHING so if this boat goes for $8K and another listed for $15-18 (and might go for $12) is loaded that could be a better deal. So do all you boat dreaming -- and break out that Book of Sin (the West Marine catalog) and then add up the cost off all the crap you see yourself dragging down the ditch and off to the Bahamas. Then compare. There are very few bargain boats at the low end of the market. Watch out for false economies.
Have fun! Make sure you buy your sweetie dinner when you drag her to go look at the boat!