Just to close this out, I ended up copying the files to the new HD keeping the same folder structure using the copy program that allowed me to verify a good copy with a CRC check of each file. When I swapped out the drives in the PC, assigned the old drive letter (I use L: ), rebooted and started up LR it functioned as normal, no need to update location or anything (so I assume LR is only concerned about the drive letter in terms of location). Totally painless.
Would you care to share what "copy program" you used. As broadly speaking I find myself in the same position..............need much large drive but I had already planned to copy to the larger drive then replace the original and using Windows Disk Management assign the same drive letter as the 'original' so as not to confuse LR.