Dell 545 MT Motherboard+CPU upgrade

Hello, I am thinking on further upgrading my 545MT (I already have 550 Seasonic PSU and AMD R7 250 1GB DDR5). I won't be doing it right now, but in some undefined time, but doesn't hurt to start planning early. I have a stock motherboard (DG33M06) with Core 2 Quad Q8200 2.33GHz and 8GB RAM. I was thinking that I could replace that with the following: 

Motherboard- ASRock MicroATX DDR3 1066 NA Motherboard N68C-GS4 FX

 http://www.amazon.com/ASRock-MicroATX-Motherboard-N68C-GS4-FX/dp/B00S8JUJLA/ref=sr_1_13?ie=UTF8&qid=1427749290&sr=8-13&keywords=micro+atx+motherboard+cpu+combo

CPU- AMD FD6300WMHKBOX FX-6300 6-Core Processor Black Edition

http://www.amazon.com/AMD-FD6300WMHKBOX-FX-6300-6-Core-Processor/dp/B009O7YORK/ref=sr_1_2?s=electronics&ie=UTF8&qid=1427750265&sr=1-2&keywords=amd+fx+6350

CPU Cooler- ARCTIC Alpine 64 Pro Rev. 2 CPU Cooler - AMD, Supports Multiple Sockets 92mm PWM Fan at 23dBA

http://www.amazon.com/ARCTIC-Alpine-Pro-Rev-Cooler/dp/B002CIDIPW/ref=sr_1_3?s=electronics&ie=UTF8&qid=1427750428&sr=1-3&keywords=amd+fx+cooler

Would all this work together (Seasonic 550W, AMD R7 250 1GB DDR5, 8GB [stock RAM, unsure if it's DDR2 or DDR3, but the Motherboard seems to take DDR2 and DDR3] and the new components listed above)? Would 550 Watts be enough for it? Will the motherboard be a right fit for the case? How hard is it to replace a motherboard in the 545? Thank you in advance.