A SSD will make the laptop feel more responsive compared to a HDD because of much higher read / write speeds. The laptop will boot up / shut down faster the same can be said for programs. The limitation of SSDs are that they are more expensive than HDDs so laptops with SSD are more expensive and they also have smaller capacity. If you need a lot of capacity and don't want tot spend a lot of money then a HDD is the way to go.
RAM is basically the easiest and cheapest upgrade for a laptop... as long as the RAM is not soldered into the laptop. A 4GB stick of RAM generally sells for $25 - $30.
Replacing a HDD with a SDD is generally easy to do, but you also need to clone the HDD to the SSD before you can actually use it. Again, that is...