PS5 external storage

So there's a few possibilities here.

You can get an internal solid state drive (SSD), which you can play PS5 games off directly. This requires a minor amount of effort to install, but follow the instructions in Sony's own video guide and you'll be absolutely fine. This needs a specific type of compatible SSD (M.2) and heat sink, but again look at a guide and you'll get all the advice you need.

You can get an external SSD, which you can use for storing games but you will need to transfer games across to the console's internal memory if you want to actually play them. This is quite similar to what you already had, just a different form of storage. SSDs are more reliable than traditional HDDs, but will be more expensive. However, it'll probably be a bit cheaper than an internal SSD.

You can get an external HDD, which is similiar to what you already have. These are more prone to failure than SSDs but they should last years without an issue, and you can get a large amount of storage much cheaper than what you'd get with an SSD.

Again, it all depends on what exactly you need and how much you're willing to pay.

You can play PS4 games from external storage no problem, but all PS5 games need to be either on the console memory or M.2 internal drive.

The internal drive installation really is fairly straightforward and just requires popping off the cover (which does require a bit more force than some will be comfortable with :)) - there's very little room for anything going wrong. It is IMO a great upgrade given the limits of the internal memory. But yes, an external drive is a perfectly valid option for storage.