Looking for a cheap cellular modem chipset + GPS
The cellular modem chip will generally not also contain the GPS, the GPS receiver in cell phones is often built into the system SoC (Nexus One) or is an external component (iphone 4).

Either way, its not cost effective to build a modem from a chipset for 1000 units, you'd probably have trouble just getting access to the parts to do so, 1000 units isn't even on qualcomm's radar.  Not only that but implementing the chipset is very complex and requires access to proper EMI/RF testing equipment and facilities.

Instead look for cellular modem modules.  Examples.

Some of these will have on board GPS and some you can program to the on-board CPU if your application isn't compute intensive.  If you need external processing you normally communicate with them via a serial bus using a modified AT command set. 

For 1000 units obviously skip talking to sparkfun and go straight to the module manufacturer, there are many out there.

As mentioned in my comments you do need to figure out what technology / bands you need to support.  The likely best option is a quad-band GSM module which should work in most places.  There are some exceptions, for instance GSM isn't used in Japan or South Korea at all.  Other countries may have some GSM support but CDMA is more commonly used.  There are modules out there that support multiple frequencies as well as multiple modes such as GPRS/GSM/CDMA/HSPA but the more frequencies and modes the module supports the more expensive it gets.  It may make more sense to design the device such that you can drop in whatever modem you want (within reason).

Talk to whatever local carrier you can find where the devices are geing installed to get the required SIMs.  For ~1000 lines you should be talking to someone at the corporate level, not the average guy at a local store.