HELP! I'm new to the forum so please be gentle.

Here's my problem
My pool is now 8 years old. When it was built, the builder installed a Hayward Northstar pool pump. The pump itself has been ok. My problem is the pump motor was replaced 3 years ago due to bearing failure. Well it's done it again. The bearings are whining away and I'm sure the motor is not long for this world. I've found replacement motors on-line for $265.00 + shipping ($29.95)
My questions are
How difficult is it to change-out and how do you change it out? (I'm fairly handy)
Do I need any additional parts? i.e. seals, impeller, etc. If so what do I need?
What can be done to extend the life of the motor?
Anything I'm missing or need to know?
The 3 year old replacement motor is a A.O. Smith Century Centurion USN 1202 2 H.P. it has the part number of 7-193687-02
Thanks in advance for your replies