Well, then the question is whether you need all those attachments. Tell him to keep the ones you don't need and renegotiate the price. Those photos indicate the implements are well-used, but decent condition and good pieces of equipment. A little better than what I was envisioning. His price is probably not bad for the whole shebang. Keep in mind, however, the engine is blown. You won't be simply overhauling the engine if it is blown. You will be buying a replacement engine. A blown engine likely means a hole in the block. A replacement engine will cost you $800-1200, depending on the engine. Check ebay and you'll see what I mean. You might be lucky enough to find an engine in need of overhaul for a lot cheaper, but then you have to overhaul it. You will probably end up finding another mower later-on for a better price, that you don't have to rebuild, and end up parking this one, or parting it out. So that means you are simply paying for the implements. So, still, the question is whether you need any of those implements.
As for the mower, if you were to part it out, you would probably be able to get a good return on your money, but it's a headache to do. Let me know if you go that route. I could use a lift and sleeve hitch for my 682!
Just my two cents...or maybe a little more.