. . . . Clearly, it'll take more than just 2 days to adapt to 5 strings -- 2 weeks? 2 months? I hope it's not 2 years (or never).
Especially tricky is when I have to use the G string -- it seems like a string too many.
How long? That's up to you and how much you want to play the 5 and how much effort you put into adapting your technique.
I took my 4 and 5 to a rehearsal the first day I got my 5. I tried to play both straight off and got in a terrible mess.
I then put the 4 string away and only played the 5. I took it to a gig about 2 weeks later. I just played it as a 4 string, but that broke the ice. It took a matter of months to feel comfortable some of the time, and a few more months to feel comfortable all of the time.
Put the 4 away. Only play the 5. Play it a lot. Play everything you know and fully acclimatize yourself.
My other piece of advice: don't think in terms of 4 string songs and 5 string songs. They are all just songs.