A1. Assume all messages are similar …  
How many total messages do you need to integrate?
A2. … or break down messages by complexity  
How many of these messages do you know to have 10 or fewer fields?
How many of these messages do you know to have between 10 and 50 fields?
How many of these messages do you know to have more than 50 fields?
B. Calculated Efficiency (more is quicker)
C. Total Man Days Estimate
D1. Source System Project Risk  
Do you have sample messages?
Is there etiher a formal specification or an XML schema?
Is the documentation public?
D2. Target System Project Risk  
Do you have sample messages?
Is there etiher a formal specification or an XML schema?
Is the documentation public?
E. Calculated Risk Rating (Higher is riskier)
Email me my calculation
I'd like to talk about this some more …