Thanks for the timely input everyone. I have decided to withdraw from the project and recommended someone else who has many years experience dealing with architects in structural matters. After consideration, I felt that while I may be competent to perform a strength analysis on the structure (a large canopy sort of thing) and can read and comprehend the IBC and related codes, I don't have enough experience with this type of structural analysis to rely solely on my own judgement.
I'm sort of an engineering jack of all trades, I own my own business and have 10 yrs experience in design of fabrications, castings, machinery, manufacturing processes, etc. I have a PE, but find it mostly useless except as a suffix to my name when writing important documents for customers.
JAE brings up some interesting topics. At what point do you assume the reader of your calcs knows what you're talking about? On one extreme you can simply state your assumptions and state whether the item under scrutiny will fail, referencing what codes you used if applicable. On the other extreme, you can write a report and show all of your FBD's for each member, explain all notation, show all steps in each calc, show EVERY calc, show load diagrams, show every safety factor for each member, etc etc. A non-engineer would have to take you on faith in either extreme, although he would be more impressed by the latter. To another engineer, the one page report is useless and the 100 page report is tedious and unnecessary.
A philisophical question: As a consulting engineer, is it best for one to sell one's opinion, ("This will/won't work"

or the PROOF of one's opinion ("This will/won't work, and here is proof WHY: ..."

? Is one opinion worth more that the other? Why? The proof of an engineer's opinion is usually greek to the customer, unless he has a another competent engineer available to him, in which case why has he hired you? On the other hand, opinions without backing are usually suspect. Catch-22?
I always thought of myself as selling knowledge, not drawings or calculations or even products. It's the knowledge of how to do something better/faster/correctly that is worth money. The knowledge benefit can be transfered to the customer in many ways, by teaching, by drawings, by a turnkey product, or by simply saying, "Do it this way and it will work. I guarantee it. That'll be $1,000." It's the knowledge that makes profit.
My almost-client and his architect were both very vague about what they actually needed from me. I got the feeling that all they wanted was a drawing and some calcs to give to somebody (the local gov. inspector?) and didn't really care what was included, as long as the Powers That Be had them to put in their files. Neither of them had a clue as to the forces involved, and their preliminary structural and foundation designs would have failed catastrophically.
Out of curiosity, once the architect has his calcs and drawings from his engineer, say, for an addition to an existing building, who then approves them? A gov. engineer? The owner? Or does the buck stop, practially speaking, with the engineer who does the calcs? If that's the case, I can imagine a number of structures are built according to simplified calcs done by an architect or in-house inexperienced engineer to lower the cost. Yikes.
Anyway, thanks again for your input.
Best Regards,
Mike