No way to avoid the process, and you should start NOW.
When a member of a RAID0 array fails, you may lose ALL your data. So if you know one is threatening to fail, fix the problem immediately.
The only secure way to do that with RAID0 is to make a complete backup of the entire drive's contents to another device. Then at LEAST do a verification of the backup to be sure it's good. If possible and you're very cautious, make a second separate backup, too.
AFTER you have the full backup, go to work on the array. Check the RAID management system you have to identify which HDD is showing problems. Then you break the array back to individual HDD's and replace the faulty one. At this point it's a good idea to do thorough tests on the other HDD unit also in case it has minor problems you can fix now. Then you re-create the RAID0 array, and restore everything from the backup.
There really is NO way to convert a RAID0 directly to a RAID5 array, and certainly no way to do the reverse. What is necessary in each case is to do the full backup, break up the existing RAID array, install the necessary new drive units, create the new RAID array, then restore the backup to the new "disk" (that is, RAID array).