Hi, Sounds like you are looking at an mc28 by the price. Is it at bridge moto in reading?
There are different models R,SE and SP all have differences. The R is a base model where as the SE has adjustable suspension and dry clutch along with the SP. The SP also has lightweight magtek wheels.
The SE and the SP are a bit more sort after and have a higher price.
All The mc28's were restricted and details of how to derestict and tune can be found on this site. I think they can cost a bit for the derestricted ignition and hrc card.
I used to own an aprilia rs250 (old shape) which was a great bike but like a lot of people always considered the NSR the one to have.
Have a look around the site it'll probably answer a lot of your questions.