Just so you's know, I have pretty much no idea about computers, like at all

So, I currently have an Acer Aspire 5740G (specs can be seen below) that is 7 years old. Bought in Feb 2010. It is a great computer, and I would say it would've been an upper-class laptop in it's day. It still runs but it's quite slow, and it's been getting slower over these last couple of months. It has quite nice graphics, when they're maxed out, but when I do max them out, the computer pretty much shits itself and won't run Sim at all (1fps lol) When I'm racing rF each week, there's aloooot of people in the one server, I've got everything on my graphics (card??) turned all the way down, and all my in-game graphics turned as low as I could. However I still get really low fps and it lags quite badly.
Now that I'm racing a bit more, I really want to upgrade it, as I can't afford to flat-out buy a brand new PC. So, my question is, where would be a good place to start upgrade wise? I asked a local computer tech guy, he told me he could upgrade the hard drive to an SSD hard drive for $200. Would this be worthwhile to get better performance, especially in sim?
Laptop Specs:
Acer Aspire 5740G
- Intel Core i3 processor 330M (2.13 GHz, 1066 MHz FSB)
- ATI Mobility Radeon HD 5470 Up to 2234 MB HyperMemory
- 15.6" HD LED LCD (I plan to get a new monitor in the near future anyway)
- 4GB Memory
- 320 GB HDD
- DVD-Super Multi DL drive