I have 2k plus 35mm color negative frames that I need to scan. ...I could probably scan everything in about a week. Does anyone know if I can rent one?
... working 24 hrs per day, no sleep, a lot of drugs, ... maybe. If you need to sleep occasionally, along with eat, shower, ... , plan on something more like a month without spending any time to do any manual adjustments in the scan. You'll still need as much time or more to clean up the images and do final adjustments in an image editor.
Second question is: Can you hook up the scanner to a computer and see it in positive? ...
Yes, if you take the time to do a preview scan. You can't afford that time if you are intent on scanning 2k images in only a week.
The third question is that somebody told me I could scan the negs on my flat bed scanner. ...
Probably not with yours, but you can with mine. The resolution (your "number of pixels") is important, but easy to achieve with modern flat bed scanners. The big issue in scanning film is the dynamic range of the scanner (AKA Dmax or density range). Few flatbeds do well enough in this respect.
You generally need a resolution of 3200ppi and a dynamic range of 4.0 to do good film scanning. You can get rather decent results with resolutions of only 2400ppi and, unless you are scanning traditional B&W negs, a density range of 3.2. The EPSON v500 (like my brother's) is a decent flatbed for film (optical resolution of 4800ppi and dynamic range of around 3.3) at a good price (generally $200-250USD). The v700 (like mine) does a bit better (9600ppi/4.0) but at a higher price ($500-600USD). The better "dedicated film scanners" (read: film only) are often scan faster than flatbeds, but don't deliver better image quality than the v700 and its sister the v750 except a few very expensive models costing 3-5x as much.