In round numbers how much data needs to be moved?
How much down time can be incurred during the switchover?
Is any of the data UTF-8?
How many different schemas are involved & how interdependent are they?
>I see some people say dbexp/dbimp is the way to go
Somebody is confused, 'cuz AFAIK dbexp & dbimp do not exist.
Depending upon answers to questions above expdb & impdb might be OK.
>and others say "RMAN convert database".
This will work.
>Are these 2 ways to accomplish the same goal?
Transportable tablespace might work?
You might be able to do it using just DB Links between the 2 DBs.
>Is there special setup needed to use RMAN?
No special setup is needed.
>Should a person who has never used RMAN stay away from it?
Not if you are willing to RTFM & practice a few times before doing it for real.
It depends upon answers to questions asked here.
You can lead some folks to knowledge, but you can not make them think.
The average person thinks he's above average!
For most folks, they don't know, what they don't know.
Good judgement comes from experience. Experience comes from bad judgement.