Agreed, it's highly unlikely that you're going to see a significant improvement going from 3 GB RAM to 8 GB. Especially if you're running a 32-bit OS, which can only address a max of about 3.5 GB.
What are you specifically having problems with that you want to speed up?
An SSD is a good upgrade for general responsiveness, and the computer will seem faster in day-to-day activities, but it won't make big Excel number crunching go much faster or significantly affect heavy Photoshop use.