@eduking.....
The question is not CAN YOU? But WILL YOU?
You have to ask yourself some very pertinent questions.
1. What you want from life?
2. Are you an ND holder just because you wanted to join the band wagon and get a degree?
3. Do you think that universities offer more opportunities and chances to graduate than poly techniques do, (From all you have heard and possibly experienced) ?.
4. Why do you want a certificate? Do you hope to get a job with it? or perhaps just for having sake?
5. Do you want to be self employed (business inclined), or do you want to be an employee?
In the past, it was easy to get away with just an N.C.E, but times have changed, the race has gotten hotter and only the strong survive. Even B.Scs, B.Eng and the likes, are not enough any more, graduates go the extra mile to get second degrees (Postgraduate certificates), as the competition has become stiffer. My honest advice, with a GP of 2.7, you seem to know what you are about, so please go all the way. Try to finish your programme, if not at your present institution, then look around you and pick one, there are so many that are good. If you want to change from poly to university, you will need to know what universities you are considering transfering to, and then visit their websites to get their direct entry requirements or visit jamb, and make all your enquiries.
With an ND, you are also sure of getting a job, but the question will then be "WHAT KIND OF JOB WILL BE AVAILABLE TO YOU?" Your choices will be largerly limited and influenced by your ND certificate. But then again, you could choose to work and school (part-time studies), so you will be gaining both work experience/ pay, and also furthering your education. The choice really is yours.
Above all, take a break, and think about what you honestly want from life. Make a list of it all and see where and how your list can fit into the scheme of things.
All the best.