Has anyone replaced the CPU fan in their Helios 18 and can comment on the level of difficulty and replacement part source?  I specifically have the PH18-72-924C.  
I've isolated the chassis vibrations in my machine to the CPU fan via manipulation of the two fans in Predator sense.  I opened the cover and indeed the CPU fan is wobbly.  The seller is offering to pay for the fan but I do not know how difficult it is to replace; unfortunately I'm traveling for work and away from the machine for the next couple of weeks.  I also need a source to buy a quality replacement fan from in the US if I decide to go this route.  
Ancillary question: are there any quieter, but still effective, fan options?  
[Edited the thread to add model name to the title]