Wow... I did a RAM upgrade less than a year ago for $40 - same capacity and frequency. Can't really fault you for that, but the RAM market sucks right now.
The SSD is a good one. I'm a fan of mine. Is this a SATA II or SATA III model laptop? If it's SATA III, then don't get that. Get THIS
. It's basically an 840 but with a pseudo-SLC write buffer for faster writes. Basically, there are three kinds of SSDs: SLC is the enterprise variety nowadays. Each cell only holds one bit. MLC holds two and is the standard for consumer drives. TLC, like the 804 and 840 EVO, hold three bits per cell. As you add more bits per cell, the read speeds stay the same, but write speeds will begin to drop. The EVO emulates an SLC drive by allocating, in potentially your case, 9 GB of storage space into a 3 GB buffer. If your laptop is SATA II, then either the 840 or EVO would be good. I'm not entirely sure, but Samsung RAPID might be available for OS X. That is a program allowing 25%, 1 GB max, of your RAM to be used as an additional write cache. If it is, then you can potentially bypass SATA II speeds for writes under 1 GB, and will then be copied to the drive itself when idle. It's available for Windows for sure, but I don't know about Macs, sorry.
The enclosure: no idea. Just find one that's cheap and reliable, really.
When you transfer data over, cloning is the easiest option. Reinstalling the OS is also an option, but I'm too lazy to do that when I upgrade. Too much work downloading stuff and reconfiguring settings. And yeah - licensed programs will work. When you clone, it makes an EXACT image of the drive. All install keys are there, cookies are leftover from your browser of choice, those prawns you've been meaning to delete are still floating around somewhere...
And finally, you sure can use the old drive for external storage, but I'd rather have the old one for a scratch disk on my desktop. Most media goes on an HDD, but a large paging file and any current projects go on the SSD for ease of access, for example. That said, it wouldn't make a bad external drive at all. Flash memory is less prone to break when dropped, and when you're on the go, that's a very real possibility. The only issue right now is $/GB for that sort of application.