Hi,
NE is not that rough as you read in the reviews, might be closer to Downtown. any area SE,SW,NE closer to Downtown is rough. This is common in any City I suppose. Its better to start from a place where you have your friends/well-wishers nearby, because the initial 4-5 weeks will be v challenging mentally & physically.
Regarding jobs in Oil/Mech industry, I don't have enough information to comment. But the general opinion here is the Job market is lot better compared to same time last year. Getting the first job is always a challenge if you are new to that place. I have meet many people who are in the job of their profession, though they struggled initially. If you have perseverance and patience I am sure you will get what you want. Also it is important to be aware of the Employer's expectation, like do some Certification related to your field, apply for the Canadian credentials etc. Getting the odd job is easier compared to Toronto.
For the rent you can browse the website calgary.kijiji.ca, which is v useful to rent and also to buy your initial stuffs. I booked my basement and bought some stuff before coming here using this site. I would recommend to start with the basement (I am still living there with my 3 kids) because it is cheaper, if you have a good land lord they are first people to help you as they are nearby you, you don't have a contract hence you can move once you are familiar with the location or nearer to your workplace. The best place it depends upon your choice, but would recommend closer to the Transit station. you can refer the website for the transit map calgarytransit.com/route_maps/route.html
Hope this information is useful.
Cheers..!