"How much did you spend?"
You have to use much because there is nothing countable here.
Many can be used when it's clear what you spent:
"How many dollars did you spend?"
You can count the dollars.
"How many hours did it take until it got finished?"
You can count the hours.
P.S: Again: Just my opinion!
Oh, now I see the thread was 1,5 years old...
Well, I wouldn't call myself an expert, but I suppose it is a relative term.
Do you think this forum has been helpful so far? Do you think you are using English more effectively because of it?
I make plenty of mistakes myself. Please point them out when you see them. :wink:
You are welcome always.