Installing memory in a laptop these days is pretty straightforward. If you can do maintenance on your motorhome, you can swap the memory out.
Before you buy the memory, plug the exact model number into a site like Crucial.com or Kingston - and see if you're ADDING or REPLACING.
You may have one slot, you may have two.
All I can share is what I'd do if I had that machine and needed to save money. I'd upgrade the RAM first.
I'd only upgrade the drive when I was sure the old one was dying and I'd NOT pay extra for SSD. I love SSDs, but if I was on a tight budget, they are clearly a luxury for me.
I like the idea of an external drive too. I haven't priced them recently but they're usually quite affordable.
For all of the external drives I have here (three) I've always bought an External Laptop HD case off eBay for $5-$6. Then I've used an older laptop drive in them. That's likely what I'd do again - buy the inexpensive case from eBay or Newegg and then a 500GB SATA drive from Newegg.
If the internal laptop drive dies, use the new one as the internal.
