As 'varkanoid' mentioned the manufacturer's service manuals usually list the compatible processors, and also any alternative heat sink/fan assemblies.
In the case of my HP they only offer one option anyway, so I think it is a fairly safe bet that this will be adequate to cater for the most powerful CPU listed, and which is sold in other countries (Australia!) as a stock option anyway!
I wouldn't go as far to say that the change is 'easy' though, especially if you are unfortunate to be blessed with 'sausage fingers', or possibly tend to be a bit 'heavy handed', as some of the components, such as the plugs and leads do have to be handled quite carefully, and it can be all too easy to inadvertently snap off or even break a crucial piece of plastic, a lug... or even a keyboard!
Some of those screws are really tiny also, so good lighting (and eyesight!) is essential. My HP manual contained a very detailed breakdown of all the stages involved, right down to screw level, which certainly made the operation a lot easier, and the fact that I have built quite a few 'barebones' laptops before obviously helped me, as in a lot of cases I knew more or less what to expect.
I am not trying to put anyone off here who fancies 'having a go', but do be aware that it is very different to working on a desktop computer... but is something which I get a certain satisfaction out of doing. Especially when everything still 'works' afterwards!
