well, the laptop will shut itself off if the CPU reaches a certain(dangerous) temperature. some motherboard BIOS have an option to set the temperature the pc should shut off at.
most BIOS will also allow you to check the current cpu temperature. if you think you are having a heating issue, open up the bios and let it sit while you have the temperature reading screen up. if your cpu is hotter than 70C you've got a heating problem.
if you want to know what the chip physically looks like, i have no idea.
CPU temps are often now based on an internal sensor on the die, and on some CPUs even report temps by individual CPU core. In other words, there is probably no sensor to identify.
Older CPUs don't have that feature and sensors may be integrated somewhere on or adjacent to the CPU.
System temperature sensors can take multiple forms, but will generally be a very small surface-mount IC. You'd likely have to read the part numbers from a large number of chips to ID the right one...while cross-referencing the P/Ns.
Temp sensors can look also like small varying colors rectangular blocks, and there are hundreds of those on a typical motherboard.
One could better localize such a search and ID the general area with a can of non-conductive coolant (aka can of compressed "air").
In my opinion, I don't think much of that repair site based on what you provided. The "suspects" are incredibly generic, some are very low probability, and they don't talk about some of the more obvious suspects for the stated problems.
A "bad thermal chip" is not even close to the first thing I'd look at to cause an over-temp condition. Look at other factors first...especially possible factors that do not generally require opening up the laptop case to investigate them. Dust/lint/blocked ventilation ports/heatsinks, failed fan (seized or 'sticking' bearing), improper ventilation while using the laptop, design defect (look for model recalls/"hotfixes"/firmware updates), system monitoring software not properly controlling the fans, improper BIOS Settings fan control values, etc.
HWA has a number of threads about overheating laptops. I suggest searching HWA (upper right corner of HWA webpage).