Just an update having recently been through this.
The upsizing wizard is good if you do not want to fully-define the new SQL database and all its constraints, but it is very temperamental - tip allocate a new empty database first and 'use an existing database' in the wizard. This ensures that the database obeys the defined default locations for the data and log files as the wizard seems to just use the data file location.
However, you should carefully check the results of the wizard, as it can forget to do 'minor' things like set primary keys and default values etc. It it does not always transfer the data, sometimes that is due to SQL being more fussy with the data, especially dates, other times it is a complete mystery. If you cannot get round it, just upsize the database definitions and then use DTS to copy the data.
DTS packages can be used to refresh the data (note that the transformations button allows you to delete the old rows being inserting new ones as the default is to append all the data!). You will find that any RI contraints get in the way of doing a global copy of all tables to SQL, so you will either have to temporarily lose them (not good) or stage the data transfer to avoid problems (e.g. cannot delete all rows from a table as it contains foreign keys used by another table in an RI relationship). Test the packages several times as you can get slightly different results depending on what steps are run when by DTS.
One last point, DBCC CHECKIDENT is invaluable for reseting your new 'autonumber' fields after playing with the new tables when you test inserts and deletes.