There was a 6 weeks gap between finishing gta3 and the release. This was needed for burning the cd and distribution. In those days you couldn't patch so there was no point hanging around. The company gave the team some time off and most people took some extra time also.
After the release, we started on Vice City. It was RockStar New York's idea to set the game in the 80s in Miami. Originally it was supposed to be a mission pack to gta3. Only once gta3 did as well as it did and Vice City started to look sufficiently different from gta3 was the decision made to make it a standalone game. This was quite far into the project. (maybe 6 months or so)
We did the PC conversion of gta3 ourselves. This took the programmers about 6 months. In the mean time the artists and level designers were able to get straight onto Vice City. This worked well as there aren't that many code changes from gta3 to Vice whereas it did involve building a whole new city and new missions. The artists and level designers used the gta3 code base for a while until the programmers were available to make code changes.
The company paid for an all expenses paid trip to Miami for the whole team. We stayed in a hotel on Miami Beach and it was a total blast. The artists brought their camera and some of them went around collection textures. Some of them spent the week in the bar next to the hotel. I caught a Dolphins and Miami Heat game.
I remember working on Vice being more stressful than gta3. There was a tight deadline (1 year) and high expectations. In addition there there was the pc conversion of gta3 in the same year. However, during this year it became clear how successful gta3 was and we got award after award. Everybody just powered through on adrenaline but it became clear that we needed a bit more of a gap for the next game.
The way of working was mostly the same as gta3. It was all about the missions. The story was pretty thin. NY were determined to up the level of voice acting and they hired loads of celebrities. To get Ray Liotta to voice the main character was huge. In those days actors still considered games a step down from movies. Liotta was prefect for the part.
It was amazing to see how the feeling of the game changed completely with just some minor changes. The weather was more sunny, the frontend was neony, the city looked more southern and the 80s music. It transformed the game.