I have Migrated from 32 bit SQL 2000 to 64 bit SQL 2005. The changes were all related to SQL2000 ro SQL 2005. I haven't seen any difference in the database based on 32bit. After migration I have taken the backup and restored in 32 bit servers. (Even Detach & attach) They all worked fine. I haven;t set the replication that way, So I am not sure how that works.
You can go with Detach and Attach (Find the files of a database, detach the database, copy the files to 64 bit server, attach the database)