Hey there, long time viewer, first time poster.
I currently have a shitty ol' Lenovo G570 which has seen better days but astonishingly, still performs, in my opinion, rather well. I've been looking at getting a new laptop until it dawned on me whether or not it is possible to just give mine a new refurbishment and possibly change some internal components within it to perform better.
I was wondering if this is possible at my local PC shop or whether someone could educate me on my options.
Any help would be GREATLY appreciated
I think the Core i5 2410M is worth upgrading. The biggest improvements from the later generations are power efficiency and beefed up iGPU's. I'm guessing battery life isn't that important if you have a 15" form factor, and the iGPU is adequate for multi-media, and some old games. The simpler upgrades can provider an excellent performance boost, mainly being RAM if you have 4GB or less, and an SSD, especially considering the G570 shipped with a particularly slow HDD.
IMO, just get an SSD, probably a Samsung 840 EVO, fresh install of Windows (or Linux) and you'll breath new life into that laptop, and will be zippier than ever before. If you have less than 4GB of RAM or less, it may be worth while to upgrade if you're a heavy multi-tasker with 40+ tabs open, but if not, 4GB of RAM is fine.
I still have my old Core 2 Duo laptop kicking, and it's still more than fast enough for everyday tasks. I have it equipped with a T9600 2.8GHz C2D, 4GB RAM, and Corsair Force F60A SSD. The biggest issue I have with it is the GPU is so old (Radeon Mobility 4650M) AMD stopped supporting it, and on Linux, I can't get proper power management (and consequently fan noise management) unless I use an old version of Linux and the ever so buggy proprietary driver. I did use it with the Windows 8 Beta to get my Mass Effect 2 fix while my main desktop computer was down. Cheap Chinese power supply didn't fair too well (started smelling it), but the laptop performed admirably. I still use it today for some of the YouTubes and general web browsing. A little loud, but gets the job done in a very timely fashion.
SSD + a clean install of the OS, and it'll feel like a new machine.
I have my lenovo r61 (typing on atm), still a brilliant unit for everything bar gaming.