Nah, switching tablets isn't that troublesome.
Especially when you go from an on the table tablet like a bamboo or intuos to a tablet with an inbuilt screen like a cintiq or a yiynova, because they're so different.
The other way around may prove to be a little bit difficult because for a tablet with a screen you can use your hand position for coordination of brush strokes, but with a tablet without a screen you won't see your hand and thus can't use that to plan out strokes. Your coordination may be a little bit off.
But worry not, getting used to a tablet without a screen will take up to a week at most if you draw a lot, and with both you can make artwork that is just as awesome as when its made on the other.
It's not like having a screen in your tablet will make you paint better
I used to work on a wacom graphire 4 for many years before getting my cintiq and had 0 trouble.
As for considering a tablet with a screen, I really suggest you really look into the yiynova msp19u because it could save you a lot of money.