99 Tarago TCR10R Heater Core Leak HELP

[s78]

Hi all, I have a strange one. My passenger side front floor is wet, Its only from halfway under the seat to about 6-8 inches in front of the seat. Everywhere else including the carpet on the side hump/kick panel and front of the floor is dry as a bone. So I really dont know how its getting wet where is is. Anyway Its getting worse and I can now hear water sloshing around when I turn and so on. I have been told that more than likely the heater core is buggered as its apparently a common problem in these models and the water/coolant is sitting in the vents etc ????? I had to put a new radiator in it a few months ago and flushed the cooling system well and truely (Maybe too well) or the flush I used didn't agree, Id say I dislodged something as I never had this problem before. Anyway If it is the heater core has anyone replaced one in this model? I've been told the whole dash has to come out and its a **** of a job......does anyone know if this is right or know if there are any short cuts that might help? Any Advice, Info, Pics Etc would be muchly appreciated. Thanks in advance, Regards Shawn