I can field this.
Firstly your questions then a bit more background info.
1) If you haven't done Methods 3/4 or Gen A 1/2 then buckle up. You're in for a WILD ride. The learning curve will be difficult (but not impossible). You go far above and beyond both Methods and Spec in this course. BUT. It starts off slowly, and the difficulty gradient is manageable if you keep up with the work.
2) MTH1040 *contains* the Spec/Methods course (except for dynamics/kinematics in spec), but does not EQUAL the course. That is, Methods and Spec are a subset of MTH1040 but MTH1040 is a much larger beast.
Now for some background info

You guys are guinea pigs!
Recently, the School of Mathematical Sciences audited their course offerings and decided to streamline the MUEP subject to fit in with the nomenclature and structure of their other units.
Together, MAT1055 and MT1085 were roughly equivalent to MTH1030. MTH1040 is now (bar a few -minor- differences) exactly equal to MTH1030. And it is now in the same nomenclature as the other first yr units. MTH1010 = Methods, MTH1020 = Specialist, MTH1030 = First Year Maths (Continuation from Spec Maths), and MTH1040 = MTH1030 for Enhancement Students.
EDIT: On closer inspection of the syllabus, some topics in MTH1040 are explored in greater depth than in MTH1030, presumably because MTH1030 is a one semester subject, and MTH1040 is a full year subject.
I believe MTH1040 has been entered into the WES (Web Enrolment System) as being equal to MTH1030 so if you continue with studies in a BSc at Monash after VCE, you're auto-credited with exemption from MTH1030 and I believe your mark in MTH1040 will count towards your degree! So that's something nice to look forward to.
All in all, it was a name change and a few content changes to more closely resemble the first semester, first year unit offered by Monash.
It should be no harder than the MAT1055/MAT1085 pairing. I think the main difference will be that while you have two exams (mid-yr and end of year), they both make up 60% of your mark for the whole unit so each exam will only be worth 30%. As opposed to previously where each exam was worth 60% of an entire unit. So it takes the pressure off a bit. But also, assignments (worth 40%) become a lot more important!
Hope this was of help.