Switching To Bigger SSD - Transfering Over Question

Hey gents,

I recently bought a 240 Gb Intel SSD to go with my rig that I built thanks to lot's of advice from here last year, [Thanks Buds!].

I have a 128 Gig SSD that is currently my C:\ drive, but I wish to make this new 240 Gig SSD my C:\ drive instead, and do a fresh OS install, plus my 2 main programs & their related 3rd party programs.

I then plan to save the current 128 Gig SSD as a back up [even uninstalled & outside of the rig], as it has all I want installed on it and working just fine as it is.

However the the programs on it are the ones that I will duplicate on the newer 240 Gig SSD, [having double the space], therefore redundant to have both installed.

So I don't want to Erase or Delete anything or Format the 128 Gig one at all. [Just stored as a working emergency back up drive.]

Otherwise, I have a 1 TB Western Digital Black Caviar HDD, partitioned into 2 equal parts, which also have OS's on them, as well as a 1 TB Western Digital USB 3.0 External Drive just for storage & back up.

So my question is this:

Can I change the drive letters and then remove the 128 SSD after the 240 SSD is up & running?

Or will this be a nightmare, should I ever need to re-install the removed 128 SSD, if it's no longer listed as C:\ drive?  

Might it be easier to remove the 128 SSD first and keep it intact as C:\ drive just as it is, and then install the 240 SSD using one of the partitions on the 1 TB Western Digital HDD as my temporary OS to achieve all this?

Thanks for your help Buds,

Jim