8174 to 9207 migration using dbua

Hi,
I am new to migration doing it for the first time,the db size is 370
gb running on SunOS 5.9 Generic_112233-08 sun4u sparc SUNW,Sun-Fire-480R i installed 9207 in different ORACLE_HOME but on same machine as the 8174 ,have free space in system (178290688 bytes) ,rollback segment free space(339722240 bytes)
and size of shared pool is 150mb which iam going to increase it to between 350m, is it enough?RAM is 32g ,database is going to be backed up(cold),do i have to change any parameters in init.ora before upgrading(dbua) ,should the database be up during upgradation or it can be down(8174)?little confused.do i need to set ORACLE_HOME for the new version before upgrading or running dbua from the 9207,any changes to be done after migration,please help me out with this.

thanxs in advance

What does the manual say?