Hello StWilson3,
Here's my answer. Firstly, yes Method can handle that much amount of information without any issues. But in terms of Importing I would highly recommend to start importing in a small batches in order to make sure importing is smooth. Here are few tips that I would like to share with you.
- Try importing 3000 customers first and see if they goes through smoothly, repeat it one more time to make sure your data is importing successfully. Once both the imports are successful, you can increase the number of customers with each import.
- If all the information is going to one table then Yes, you can definitely do it in one shot by putting the value in the corresponding fields of the Table. For more info please refer to this video Tutorials on Importing/Exporting Customers
- Unfortunately, there is no estimated time for the process, but if the number of records are more it is likely to take long time. Once you complete your first batch you will get idea how long it will take to update all those records. (Please do not try to update huge number of records like 10,000 or more.)
- As far as importing is concern, browser palys an important role. Mozilla firefox is very reliable browser and we never come across any issues while using Mozilla Firefox.
-Inder