Amie
Mac Convert for Life
Worst case scenario (assuming removal of battery, power, and basic grounding), the memory doesn't work. Take it out, and you're up and running again.
It's probably slightly more risky than replacing your laptop's battery.
While it's a good idea to not invest too much in your laptop, a new (apple) laptop will cost at least ~ $800 (refurbished, of course). Assuming that lasts 5 years, you would "spend" $160 per year (plus applecare, batteries, etc). If you think this upgrade will give your laptop another year of life, it's probably worth it.
Another YEAR of life??? My laptop is only three years old and showing no signs of dying any time soon. I expect it to last me at LEAST another five years. The computer I had before this one lasted me 10 years ... and it was a PC.