Hi

You don't need to connect to the prod database.
You need to have the dbid stored somewhere if you dont connect to the RMAN catalog .
No it will not touch the prod database at any time.

Yes there is a function in 10g from which you can scn_to_timestamp and timestamp_to_scn

But if you know the time to which you want to restore you can use that directly in RMAN using set until time syntax

regards
Hrishy