So after a few days, the machine was running ok, though slow clunky and hot - just one task would make the fan go fast and loud, istat menus told me that the CPU was at about 80c and the fan was running at 6800 when the machine was doing almost anything...
Applying new thermal paste and cleaning out the heatsink and fan is probably the best, fastest and cheapest way to prolong the life of your machine and boost performance. iStat menus is a great system monitoring application, but for fan control my go-to app is
smcFanControl, as it's the easiest and most convenient way to manually adjust and set fan speeds. And it never ceases to amaze me how horrific the factory application and use of thermal paste was on their MacBooks and MacBook Pros during this time period.
Due to an odd
quirk of the Intel
i945 chipset used in the pre-Santa Rosa MacBooks and MacBook Pros (i.e. the MacBook/Pro 1,x and 2,x), the system hardware recognizes only ~3.3 GB of RAM if 4 GB is installed. Apple and other manufacturers responded to this by only "officially" supporting a maximum of 2 GB RAM in these machines (despite the fact that they take 4 GB of RAM just fine), while other manufacturers actually stated that their machines could take 3 GB of RAM.
As for streaming video I always run Tampermonkey with the "
Disable YouTube 60 fps" userscript, which forces YouTube to run at 30 fps. Sure, I'm not watching 4K or HD video, but given that I'm running hardware that is 15 years old, I'm willing to make some concessions for modern internet useability.

And depending on how far you're willing to go, you could replace OS X with a Linux to get access to more up to date web browsers.
I just love to work with these machines. Accessing the internals is a breeze. (People complain about all of the screws needed to remove the topcase, but that's nothing compared to many comparable consumer Windows laptops of that era, which often required a near teardown of the entire machine to gain access to the motherboard.) They're incredibly versatile. In addition to running Windows, 10.6, 10.7, or 10.8, you can also use a lightweight Linux distro like Zorin, Xubuntu or Lubuntu. Not only are they great tinkering machines, they're also fantastic for retro Mac gaming and Windows gaming via WINE.