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

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  

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