Hmm...ok, to fix eberything one go future no more headache do as follows :
1)Get a H700 Processor(H701+RUX-C701 if you want the new model)
2)Get the VCD changer VPA-S001 or DVD changer DHA-S680E
I think you need to get a AV interface for your LCD Screen as well.
The 7998R will be connected to the H700 or H701 via the fiber cable OR Ai-Net.The VCD and DVD changers will alos be connected to the H700/H701 processor via Ai-Net as well and the processor unit will end up as the control centre for your AV volume,EQ,Xover, TA and so on.
One thing i am curious, did you consider VCD or DVD in the 1st place when you thought of buying the 7998R? because if you did, then a IVA-300 would have suited you more.
But end of the day a 7998+vcd/dvd changer+processor+LCD screen would have cost more than an IVA-D300(i heard about rm5k+).
Cheapest solution for you now would be to buy a chap ayam vcd player and run it independently.