I will dispute the 4 or 5 hours to train for an SEP class rating from TMG. My advise would be to go to an ATO that understands TMG and NPPL SLMG training.
As a HoT, I would be very surprised to see a successful test without more training. In fact, to complete in this time would be non compliant with our approved training manual (not so if converting SLMG to SSEA).
I notice that you say you have a Class 1 medical. Does this mean you want to end up with a CPL? If this is the case you will still need time in an SEP as TMG/SLMG hours don't count for CPL licence issue which has caught people out before.