Change class or long break?
You can try out in Heart of the Mists (PvP) whether or not you like the feels of any of the new specializations. If you have Heart of Thorns, all of the specializations are unlocked there (remember to use the 3rd line).
As for levelling the new character:
If you already have a character that is 1, 2 or 3 years old then you get a tome which will bring your character level up to 20 (or 30 for the third birthday), maybe this can help you? You can also get Tomes of Knowledge which can be used to gain a level (get it through the daily login rewards/sPvP/daily WvW or check the wiki for a list of all options).
You can’t buy max level.
You can try what TwanBr suggested, use the level 20/30 scrolls to get started and then use tomes and writs of experience to make leveling go faster. Crafting will also give you 7-ish levels for each discipline from 0 to 400. With a level 20 scroll, you should be at or very close to 80. Costs a lot of gold, though.
I don’t remember all the details about Reaper from the beta, but the “turning black” should be death shroud? Which is something you have to activate, it doesn’t happen automatically. I mean, it’s a core feature of the necromancer class, but you can ignore it if you wish. Or turn your graphics settings way down, maybe that gets rid of the effect.
And maybe just try out leveling now. It got a major overhaul a while back. A bunch of people (myself included) hate it with a passion and wish we could go back to the old leveling experience, but since you hated the old one, maybe the New Player Experience is more fun for you.
As for the “being herded to your goal” thing… that doesn’t exist here. The new maps are designed as a whole, as in, you need to know what’s ging on on the entire map to know what you’re supposed to be doing. That’s not going to change for the HoT maps (I hope), though you’ll find any new toons you make will be bombarded with not-so-subtle hints about where to got and what to do. Might be more up your alley.
Kaerleikur @ Elonaspitze