gta iv episodes for ps3, will it need a install

i know rockstars only just announced it but it still makes me wonder how much data i need to install for the two add ons if i get the disk version i also wondered how did they manage to get both episodes onto one disk for the xbox because i remember them saying they ran out of disk space for the original gtamdogg91

It would be like any other dlc addon. It is still in Liberty City, isn't it? So they just add the data that isn't in Liberty City already, and there you go. I would say 4gb for it, but that is guess, and it could be wrong.

do i need to own the original if i want buy the episodes in disc form

I understand that the PS3 versions will mirror the model they used for Xbox.. So yes you will need a copy of GTA IV and then either download the content you want to the PS3 disk or buy it on a installable PS3 Blu-ray disk.

Shouldn't require much space