All pins of the Arduino (except XTAL1,XTAL2 of the Atmega 328) and the XBee are provided on the headers, which have a standard 2,54mm spacing.
The Arduino and XBee are only sharing the power supply. If connections are needed between the XBee and the Arduino (e.g. TX/RX) or anything else ,wire bridges can be made between the header pins.
The board has SMD/SMT parts. Solder paste and a Hot Air SMD Reworkstation was used for Soldering. The Trick is to use as little solder paste as possible. I applied the solder paste to the Board cleaned the pads with the top of a scalpel.
Parts used (Digikey Numbers):
LDO SPX3819 (1016-1248-ND)
CER RESONATOR (490-5994-1-ND)
59Ω Resistor (P59.0FCT-ND)
10.2KΩ Resistor (RMCF1206FT10K2CT-ND)
Tantal Capacitor (399-10116-1-ND)
The Power supply has a current output of 150mA. Next time I will use a SPX3819(1016-1248-ND) which can output 500mA.
Update: The SPX3819(1016-1248-ND) works better and was added to the part list as a replacement for the LDO (576-1259-1-ND).