Comeback after "thousand" years

Hi, I am getting back to wow after TBC era...I am PvP/PvE player

- on TBC got brutal gear also with weapons as a rogue...- on pve owned raids with my guild as a heal priest and got from KJ to BT and defeated Illidan

so I would say I am pretty experience in TBC...

This is the first time I want to try Wotlk, but got no idea where to start...I am pretty sure there are big class differencies...so if you got any tips tricks for me I would be grateful...

I want to focus on PvP, but also I dont want to miss PvE and as a warcraft fan would be honor to own ICC and Arthas (and then cry a lot about his sad death
:(
... I am thinking about playing Warrior, or trying something new like Retri/Holy paladin...something that I could switch from PvP/PvE anytime...
i heard there are thousand of paladins out there which kinda dismotivates me to play him.....as mainly focused on PvP trying to get high arena rating etc...gearing up and those things...which is the better choice for icecrown? or any other class ideas?(not looking for unbalanced easy gearing class,but something flexible, funny and also high skill - high reward)

Thanks