Yes, you can take a SIM card out and still have navigation as long as you have preloaded the maps for the area you are driving and have activated your Voice Guided Navigation licence (assuming you want Voice guided navigation) The lock to satellites can vary according to differing factors including weather, terrain, whether you are surrounded by tall buildings or not.
I can usually get a fix within 2-3 minutes with clear line of sight
Using Nokia Maps offline is one of the big benefits over using Google Maps, especially when roaming. The maps vary in detail I've found but it has been a year since I last used Nokia Maps over seas. I recall that when the NZ map was released it underwent several significant revisions as more details was added.
I reckon 2-3 minutes to get a fix on newer hardware. On older devices such as the N95 you may be waiting 10-15 minutes (or never). That's been my experience at least.