1) Would I still need to mindlessly grind on mobs to level up so that I may get to pvp? How long would it take me to reach max level in order to start enjoying pvp with a group?
Yes. How long it takes is dependant on how much you grind. However, I can tell you that getting to 50 (which was the old cap when you were here) will take a week or two. Getting to 60 (the new cap) will take a couple months though. You can war easily at level 50 and do pretty well, but I wouldn't advise trying to pvp a lvl 60 because there stat differences between level 55+ gear and level 50 gear is pretty significant.
2) Is this game gear dependent? FOR EXAMPLE: At high rank, will someone with orange gear get beaten by someone in purple gear despite the guy in orange having better skill sets and tactics?
This is the only MMO I have played, so I am not quite sure how that would work, but no, it isn't. Example: Yellow (special) gear with better stats than purple (epic) gear is better than purple (epic) gear. However, Special gear only gives one bonus, epic gear gives 3. So, in general, epic gear will probably be better.
3)Is this game pay to win? I know there is a cash shop, but does it give you a significant advantage against others or is it all cosmetics? For example, does everyone get a basic mount? if not, I would see that as an unfair advantage as the people who payed real money for a mount have greater speed while the other have to walk. I.E. catching up to enemy or getting to location X before them etc
The game use to have mounts for golds, and they need to bring that back, but NGD put mounts only on the cash shop now. The cheapest one (which has the same speed as the others, the others just look better) costs ~5$, so, although not too much, they should still be able to be bought for gold, in my opinion.
4) How is the community in game? the Clans? Leets vs Casual gamers?
Community is pretty good, it is the only thing that is keeping the majority of us here. Depends on what clan you join, but they can be fun. Not sure about the last one, but there are more casual gamers than "leet" ones, and a lot of players who suck, but think they are pro coughelvacough 
5) If i decide to join, which server would I go to? which side? Any side that is the underdog? if so why?
Also, which class? I seem to like barbarian so far but 8 years ago i used to play KNIGHT. If my knight is on a spanish or german server and I would like to bring him on a english server, would this be possible? ( I forgot where he was stationed)
If you live in an English-speaking country, your server would be Haven. The underdog right now is Syrtis, iirc. Not sure how they became so underpopulated because they use to have double-quadrouple the amount of both the other realms combined, but karma I guess. Anyway, the underpopulated cycle goes around every year. Right now Alsius is OP. Next will probably be Ignis, then back to Syrtis, etc. So, I would say choose whichever realm you prefer. Im in ignis, so, if you want to show me your tits and/or have sex/an orgy, feel free to join there, and let me know who you are.
Depends on your style of play.
I know they use to allow RA (spanish) transfers to Horus, but that was a long time ago, and Haven is the new English server, so you will probably have to send in a support ticket about that.