how to perform large number(128bit) division

You can use Newton method for computation of 1/a and then, use it for division computation.

In case if you computed x=1/a with 64 bit precision, you can improve it to 128 bit precision with simple formula: y=2*x-x*x*a.

You can generally start with 4 bit 1/a approximation and apply this formula 5 times, then you can implement everything from the scratch without megawizards on integer arithmetic (do not forget to scale your intermediate data!!) and then convert to floating point.

Sure you can make it fast enough with pipelining. I did it once for my Stratix III project and achieve about 250 MHz, probably it can be faster but it was enough for me.