Mit42, va_land & experts: REO addendum question

I signed a 4 page simplified contract when make offer to a bank owned house. banak countoffer back then I countoffer again. Now bank accepted my countoffer and ask me to sign a addendum. this doc basically protect seller (sell AS IS....). Should I sign this addendum? Is this the normal step for REO? Are we going to sign a standard 11 page contract later?

thanks.