We're assuming it is a chipped machine so the locking/unlocking HDD question is likely irrelevant. The HDD only needs to be locked if it is a softmod. As
shloader has said, you seem to have done the first part: installing a dash to the new HDD. AID or HeXEn would have been better than the aged Slayers but there is no reason for that to be the cause of any problems.
The question really is just how to get the contents of the old HDD onto the new one?
As
shloader also suggested the easiest method would be to FTP everything from the old HDD to a PC and FTP it back to the new one. But you can also use Chimp 261812 to do it direct. It will 'simply' clone the old HDD content and structure to the new one. If the old HDD was working as you wanted then that's what I'd suggest doing. It won't be as quick as FTPing but it will probably be less trouble.
You actually do not need to install a new dash to the new HDD be able use Chimp, in fact it is often recommended the new HDD you're cloning too is either virgin or wiped clean first, although that is not essential.
https://www.youtube.com/watch?v=lBC9599ww6I
Once the old HDD is cloned you swap the new HDD in remembering to change the jumper setting to Master from Slave first.
The only problem I can see with using Chimp is the F:\ drive formatting and that will depend on the size of the new HDD. The F:\ drive (and G:\ if used) must be correctly formatted if it is larger than 256GB. Cloning F:\ from the 70GB old HDD will mean that it is formatted for 16K clusters.
Later reformatting of the extended partition(s) for 32K or more, depending on the HDD size, will wipe the cloned F:\drive content, which is a bit of a problem.
So if that is the situation in this case I do not know if there is any way of using Chimp to clone the F:\drive but with the correct cluster size for the new larger HDD. Rocky5 will be able to explain if that is possible but you might be better off using the FTP route instead.