Lots of questions on the forum re Diag and the 5AM and 59AM ECUs
Leads are found on ebay Two are required a blue one like this;--
VAG GROUP USB COM PORT OBD2 II KKL ECU DIAGNOSTIC CABLE LEAD VCDS-LITE 409 DO NOT USE ANY SOFTWARE THAT COMES WITH THIS LEAD
Instead download the correct driver from JP's site.
and one like this;--
Fiat 3 pin OBD1 OBDI to OBD2 OBDII Convertor Connector Auto Scanner OBD Lead with flying +and- connectors
These are around £20 the pair.
The Software is FREE at http://jpl250rs.perso.sfr.fr/ To get your licence follow the instructions to register your Ecu, then you will be able to use most of the program, Including resetting of service icon.
Do take time to read up everthing on JP's site. Also try Guzzidiag where instructions on re flashing are available.
Remember that you play with your ECU at your own risk. Please don't fry it by not following JPs advice.
Last words, never connect pos and neg round wrong way!! Always do a lead connection test before trying anything else, it's on the software (Connection test) Tab