Does anybody know where I can get the assembly guide for Monograms 1/24 scale Ferrari Testarossa Convertible (Kit #2782)?

Here is the link for Revell-Monogram instructions-

http://www.revell.com/support/instructions.html

I didn't see your specific kit number after a quick search, but R-M re-issues their kits under diferent numbers-you might want to start at the top and serch for a Ferrari Testarossa and find the same kit but under a different kit number

Good luck

You could look up the kit plans on the internet and download them or you can look up Monogram Customer Service on the net and give them a call.  I've gotten good service on replacing missing parts from them.

Jim