Marhaba =).. I personally used the Kaplan OAT book that I borrowed from my friend with out taking the class, along with the OAT topscore and OAT Acheiver CDs, and a little from the MCAT Crackers, and I've done well..
If you can set a time and schedule for you to study and stick with, then I think you should be fine..
For the Site that you put, me and my friend bought it and it was totally useless, It was a rip off, but they were kind enough to give us a refund back.. so dont get it, it is totally a waste ..
wa inshAllah kel shee bkheer
good luck =)