CFI Training 7: I'm ready; Is the plane?

I've been ready for my test just trying to get the spin sign-off  and then schedule the test. I was hoping to have the certificate by the end of April. The RG I'm use to flying was nearing it's 100hr inspection and it's annual. Additionally it's been throwing some oil and the engine was surging a bit, so the maintenance crew decided to tackle all three at once, rebuild the engine. This is going to take a full month. I decided to find another RG to use. Ideally a 1980-1984 172RG as they are most similar to the RG I'm most used to. I found one at another airport an additional 1hr south of my home base. Before getting checked-out and signing the rental agreements, I specifically told the renter my needs and intents, asking about time to standard maintenance. I was told it would be no problem as the plane had plenty of time left. Today I found out that the RG was really going to go under maintenance right away, needing three weeks off. I just spent $180 for nothing. I'm a bit upset. Well, I guess I'm off to find another different RG to fily for the test.... Oh, well, the spin-sign-off is scheduled for tomorrow. Hopefully the weather holds out.