I am a n00b planning to assemble my first PC. I have narrowed on AMD Phenom II X4 955 Black Edition processor. However somewhere on the forums I read that AMD processors do not ship with Heat sinks. Do I need to buy a separate heat sink. If so which one should I buy. I do not plan to overclock the processor.

If you buy the retail (or boxed) version then yes it will come with a heatsink. Just don't buy an oem or tray item, they do no come with heatsinks.

Now i could be wrong but from what ive heard it actually comes with a pretty decent one with heatpipes and the works

-------------------------
CPU AMD PII 1100T @ 4.0Ghz w/ NZXT Havik 140 HSF
Mobo: MSI 790fx-GD70
RAM: 8GB Kingston HyperX LTE
Vid Card: ATI HD4870 + 9800GTX+ PPU
HDD: WD Caviar Black 500gb x2
Case: Corsair Carbide 500R
PSU: OCZ Fatal1ty 750w
MS/KB: Roccat Kone+/Razer BlackWidow Ul

depends on your ambient temps

-------------------------
Setup:-
CPU: AMD Phenom II X4 955B.E. 3.20 GHz
MB: Asus M3N78 PRO Rev.1102
PSU: OCZ StealthXStream 700-Watt
RAM: Corsair Dominator Dual Channel 4096MB PC8500 DDR2 1066MHz Memory (2 x 2048MB)
HD: Western Digital 320GB
GPU: EVGA GeForce GTX 280, 1GB GDDR3
Case: NZXT Tempest
OS: Windows XP Pro (SP3) x32-bit

I highly recommend this heat sink with OCZ Freeze thermal grease. I had the stock heatsink and my temps at idle were in the low 40's and under load low 60's With this your temps will drop 10 to 15c. I'm now running at idle 26-30c. and under load 50c.
http://www.newegg.com/Product/...x?Item=N82E16835118223

-------------------------
Processor: Phenom ll 1090T X6 @ 4.2 1.50v On Water
NB: 2964
HT: 2117
Motherboard: Asus Crosshair Formula IV 890FX
Memory: 8 GB Gskill PI 6-8-6-24@1700
Card: Msi GTX 580 900/1800/2048
HD: 3 WD Caviar Black 500 GB Raid 0