The stock HDD that came with my MacBook Pro was running a bit slow and consistently added a lot of heat inside the laptop, so I decided to switch it out for a 256 GB SSD from iFixit!
It went perfectly! I followed the guide on iFixit's website and didn't have any problems!
I was incredibly nervous about using SuperDuper, but it ended up being very simple and straightforward
The drive replacement took about 30 minutes, mainly because I was nervous and kept having to wipe the sweat off my hands. Taking out the screws on the battery and HDD were the toughest part. Those suckers are small! But I used the tool kit that came with my new SSD and eventually got it done.
All in all, however, it went very smoothly and was nearly stress-free! I highly recommend using guides from iFixit.
The advice I would give to anybody wanting to try upgrading their computer hardware would be to just do it. I was almost going to spend $2,600 on a new MacBook Pro, but ended up doing my research and didn't even spend $400 on a solid state drive and brand up DDR3 RAM (admittedly got the RAM from Amazon...sorry iFixit team :P). My laptop runs better than it ever has and doesn't even come close to heating up as much as it did before I installed the upgrades.
Put simply: don't throw away a perfectly good laptop just because you want some new eye candy or because you don't think you're qualified to tweak your current system. It's a great learning experience and there's nothing more fulfilling than successfully booting up an old computer with brand new parts inside.