You can download the software free from rosstech website, so just need to buy the cable..
Ross-Tech: VAG-COM: Download old versions for obsolete interfaces
The freeware version is good enough for diy diagnostics/resets etc but you wont be able to remap the ecu from it...
For remapping you will need a flash tuning box kit + tuned files from a reputable source at least + a program like winnols, i looked at doing this myself last year and trust me its easy to bugger a ECU if you dont know what your doing ...