Dave:
I'm heartened to see Wachovia pro-actively working with their upside down but performing borrowers. It means the banks and the investors holding the paper are finally being realistic and working through their problems. Once this process is in place, the market value of all that paper floating around will become easier to determine and the banking system can finally begin to recover.
How I would value what the bank is offering you is to do a discounted cash flow analysis on the payments the bank will receive on the second. They will receive no payments for the first three years, and then they will receive monthly payments of $176,000/(27x12), or $543.21. Discounting that flat revenue over the 27 years at a market rate of 6 percent (0.5 percent per month) gives a value of $87,055. Discounting that lump sum for three years on an annual basis gives a current value of $73,093. Someone out there may have a different opinion of the appropriate discount rate, but the principle is the same.
From a financial analysis viewpoint, the bank and investor are willing to accept the principal on the new market rate first at $241,600 plus the discounted value of the second at $73,093, or $314,693 instead of the $409,000 you owe. That's a better deal for them than foreclosing and getting $250,000 and paying all the costs of a foreclosure.
In your shoes, if I felt I could manage these payments and the house would likely be worth at least $314,693 plus selling expenses at the end of my projected holding period, I would seriously consider the offer. It beats the alternative of a short sale or a foreclosure. I would also try to negotiate the rate on the first before I agreed, as rates continue to drop. If the offer was made back in early November, you should get a better rate today.
Good luck, and be sure to apply the lesson about the plusses and minuses of leverage from this experience in the future!