You won't have access to the first class lounge. I think the first class lounge is only for first on international three class aircraft (similar to the "transoceanic" requirement for drink chits at the RCC).

On a trip earlier this year in F to SXM (St. Maarten) I was denied entrance to the ORD International F lounge and was told to use the RCC. I thought this was the case before attempting to get into the F lounge, but it was at least worth a shot!