ORA-48108 & ORA-01034

I'm trying to set up a database on a Solaris 10 platform that had its database corrupted before. Due to the lack of backups, I was forced to reinstall Oracle server. Currently I'm facing an issue where answers I have found keep sending me in loops. I opened sqlplus, and saw that it was connected to an idle instance, so I performed the STARTUP command. This led me to the following errors: ORA-48108: invalid value given for the diagnostic_dest init.ora parameter ORA-48140: the specified ADR Base directory does not exist [/export/home/oracle/u01/app/oracle/product/11.2.0/dbhome_1/dbs/] So after some googling, I was told to try changing the diagnostic_dest via the following: ALTER SYSTEM SET diagnostic_dest='u01/app/oracle';, which was equivalent to setting the diagnostic_dest to my ORACLE_BASE. However, the error below occurred: ORA-01034: ORACLE not available After some googling again, I found that the solution was to start the database (which I can't)! I have no idea how I should proceed from here. Any help will be much appreciated. If any other information is required, I will gladly update it in the OP. I have tried restarting lsnrctl, but it doesn't seem to help. I would change all the default parameters within the file locations, but from what I found, the init.ora file which was supposed to be used already has diagnostic_dest='', the spfile.ora file also has diagnostic_dest='/u01/app/oracle'. I'm really lost as to how I should carry on.