"also I'm curious if there are any good farmin spots in northrend for an engineer?"
Prime Spot for Engineer is in Wintergrasp at the Cauldren of Flames.
Mining Veins (Sar & Tit)
2 "Fireballs" to use your Mote Extractor On
Lots of Fire Elementals to kill for crystalizzed Fires
Then hop down to the Maw in Dragonblight and grab a 3rd "Fireball" then head towards the "Snowball" nearby to the NE, rinse and repeat.
"Other than the "Fireballs" and "Snowball" what does any of that have to do with engineering?
There're the mechanicals in Borean Tundra, and around the library of invention in Storm Peaks, but they don't respawn at all quickly, and rarely give anything but greys.
There are also mechanicals in 5-man instances, but to farm any of those efficiently you'd need a group.
I don't believe you can "skin" mechanicals pre-northrend, otherwise Mechanaar would be a good spot to solo. I thought I saw a pickaxe in AQ40, but it may have been a fluke.
That leaves Ulduar. It isn't too hard to 4-man Leviathan, We did it almost by accident while waiting for the other 6 players. "Let's just clear some trash up to Leviathan while we wait." XT requires more people, and there're 2 statues right after him that are "Skinable". Someone told me you could 2-man Levy, by jumping between seats on your demolisher to shoot down pyrite. It seems Levy ignores demolishers if there's no driver. I'd expect him to reset or evade if both demolishers were driverless at the same time. Ponging him this way is a banable exploit.
Unless you're after the plans for jeeves, I'd say it isn't worth the time killing anything but Leviathan (even that's probably not worth the time due to the falling titansteel prices) unless you need to farm there for some other reason as well.