mssoftness

Good Morning All,
Hope you can help me with this one. Here goes: I have a 2009 RX8 and started feeling something under my front tires while driving. It's not making alot of noise, but its not running like it use to (smooth). I took my Baby (that's her name) to Mazda dealer. They diagnoised it to be: hub & bearings - the front driver's side and passenger side. He said that I can still drive it, but soon I will hear some noise. I have 64K miles on it. My co-worker said that hub/bearings should last at least 150K miles and maybe the dealer told a lie.
The price dealer gave me to fix it: $1139. which includes tax and wheel alignment.

My funds are low and about to get layed off soon. My questions is: how can I tell if the dealer gave me the correct info? Also....Is what my friend told me about the 150K miles correct? What is the cheapest but correct way to do this? Do I buy the parts and take to a mechanic? How much will the parts cost?

Thanks so very much. I appreciate your answers.
Ms. Softness