buying and selling real estate

as far as real estate can be considered real property in china, that is.
Wife and i own an apartment, we are selling it and buying a newer, bigger, nicer place. (Yayyy!) The thing is, well, actually there are a lot of things, but one just came up. Although the apartment we are selling is in my wife's name, the real estate board will not permit us to sell (or, if i understand correctly, which i may not, buy) unless we provide proof that my wife and i are married. well, we have the marriage certificate, but we have been married for 10 years now. The passport number on the original marriage cert is the number of an old, expired passport. (I have a new one, thanks for asking) Seems the Chinese can't get their heads around the idea that the number on the passport is the number of the booklet, not of the person. So we have been instructed, in that marvelously opaque Chinese manner, to obtain from the Cdn embassy, proof that I, the holder of current passport number xxx++ am acutally the same person as the holder of expired passports xxx+ and xxx.
Has anyone else had to do this? When I go to BJ, will the people at the embassy be helpful, or will I get a "So what do you want me to do?" answer?

I've dealt with the same issue, but with regards to my kids' birth certificates. Chinese people just figure everyone has an ID card and an ID number and the idea that the number might change is, as you said, pretty mind blowing to them.

I keep that old passport with me just in case. The embassy in Beijing should be helpful though, as they have undoubtedly encountered this issue before. You're an American, right? In general, I find citizen services part of the embassy to generally be really polite, helpful, and efficient. No comment on the other departments!

Oh my.

Related question - do Chinese passport numbers change when they renew passports?

I wonder if, when one's passport number or anything else changes, it is possible to head down to the Chapel of Love Bureau of Harmonious Family Relationships to acquire updated marriage certificate booklets.

no, canadian. I have found embassy staff to be very polite and helpful once I know what to ask for and have everything they require, but knowing and having are not always easy. Seems their communications branch has been copying the Chinese operations manual on obfuscation and delay

I was at the tax office as part of step 5 (of many) to get my name added onto my lovely wife's local apt, so took the chance to ask about changing passport numbers.  The clerk told me that it was very important to keep the old passport.  Not sure what happens if they old passport is lost.

update. The Canadian embassy was verrrry helpful.  understaffed and overworked, but the staff they had were polite, professional and as helpful as anyone could ask them to be. They are doing a lot of these, so once I gave them my story (short version) and old passports, they had the letters done up in about 5 minutes.  
Unfortunately, I managed to mess up one important detail. I emptied my working account and took cash, which hotels accept but the embassy doesn't. Fortunately, someone else who was waiting for the same thing had plastic, and offered to cover me. I gave her the cash, she covered me, and everyone was happy. 
BTW, flying DL to BJ took 4 1/2 hours, if you include delays. The dongche (fast train) back took 6, no delays, arrived on schedule. Guess how I'm going to BJ next time?