I did it and have had no issues with the fuel gauge. I've put two different clusters in mine and both read correctly. The key is to find one from a C2 Carrera, a Cabriolet if at all possible (that way your top open light will work upon installation). It's a straight forward swap and if you can pick up the Carrera gauge pod with the cluster, it makes it even easier. (Your Boxster pod will work with some trimming.) Keep in mind that if your Boxster is a 2000 or earlier, you will need the cluster from a 2001 and earlier C2 Carrera, if it is a 2001 or newer Boxster, you will need the cluster from a 2002 to 2004 C2 Carrera. There is also the issue with changing the mileage of the donor cluster to match the mileage of your Boxster, which isn't cheap to do (see the thread ToolPants gave you the link for). The dot matrix display rocks!
I know, I need to vacuum the carpet.