Beginner

I'm from VietNam.I want to make a RepRap to graduate the university.I have 6 months and 500USD. What should I choose RepRap type ?
What is the most difficult in RepRap ( extruder or program for electric circuit) ? And What is software to program ?
Thank you

I was able to make a Prusa I2 with a heated bed for well below that amount ($450) with my own printed plastic parts.

I haven't plastic parts.In Viet Nam also haven't.I must buy in foreign country.500USD maybe not enough ?
What is the most difficul for RepRap?

my shopping list for Prusa Mendel i2 : (with shipping fees)

$70.00=Printed Plastics
$58.71=5 PCS Wantai Nema 17 Stepper Motor 42BYGHW609
$5.50=10pcs LM8UU 8mm Linear Ball Bearing Bush Bushing
$152.50= full electronics set
$8.70=3pcs 5x8mm CNC Motor Jaw Shaft Coupler 5mm To 8mm
$28.99=T2.5 Aluminum Timing Pulley + Timing Belt 2m
$8.88=Hobbed bolt M8 for Wade extruder - prusa mendel reprap
$58.74=hotend J-Head Mk V-B
$55.00=Smooth Rods
$31.30=DC 12V 30A Regulated Switching Power Supply 360W
$30=Nuts, Bolts, Washers &Threaded Rods bought at local store
$10=6x 608zz

Total $518.32

Stas Wrote:
-------------------------------------------------------
> my shopping list for Prusa Mendel i2 : (with
> shipping fees)
>
> $70.00=Printed Plastics
> $58.71=5 PCS Wantai Nema 17 Stepper Motor
> 42BYGHW609
> $5.50=10pcs LM8UU 8mm Linear Ball Bearing Bush
> Bushing
> $152.50= full electronics set
> $8.70=3pcs 5x8mm CNC Motor Jaw Shaft Coupler 5mm
> To 8mm
> $28.99=T2.5 Aluminum Timing Pulley + Timing Belt
> 2m
> $8.88=Hobbed bolt M8 for Wade extruder - prusa
> mendel reprap
> $58.74=hotend J-Head Mk V-B
> $55.00=Smooth Rods
> $31.30=DC 12V 30A Regulated Switching Power Supply
> 360W
> $30=Nuts, Bolts, Washers &Threaded Rods bought at
> local store
> $10=6x 608zz
>
> Total $518.32

Where can I buy?

make a Mendel Prusa, success is much or little ( because this is graduate).I don't know much about program.I fear I will not program.