Welcome to the Club!

Prusa i3 - my personal experiance getting a kits and assmbling it only took 1 whole day , configuring it will take another few hours, note I have configured few 3d printer before so software part was a breeze, first timer maybe will take a bit longer but still depends 

Mendelmax 1.5 - is a good printer too need more time to assemble and it have a very sturdy frame 

Kossel Mini - only if you are up for some challenging build and software calibration  

or if you have some money to burn there are a few other ready to print 3d printer like flashforge/CTS (makerbot 2 copycat)

Hi, eehtsitna
You may consider the followings:
- Filament choice: if no heat bed, you might only able to print PLA only.
- No upgrade for dual extruder for two colors in future.
- Kossel mini have only 3 motor to control XYZ axis, of course cheaper prize.
When goes to fine tuning, you might not know which axis goes wrong mechanically.
Unless you are good in programming and know how to calibrate well using the probe.
As a comparison, Prusa i3 at least one stepper motor for each axis, when problem arise,
you will easily troubleshoot the problems.
- Size is a matter for beginner. You can print bigger size, mean you can tolerate/compromise with its bad accuracy.
As a beginner, you will easily upset when you cannot print small part nicely during the calibration process.
- Bigger size means more rigid. More rigidity means you could print a little bit faster and less troubles.
- Pay more for one stepper motor, heat bed, bigger size and rigidity and the most important is less troubles.

There are tons of PROS and CONS. As a beginner, just my personal advise, choose your printer wisely.
You might not agree above, you can choose Kossel mini, not a problem.
Or you might choose Prusa i3, and print parts of Kossel mini eventually...
The choice is yours.

Congrats to you, at least you make a great start in this new year! And welcome to the club...
You will spend lots of times to setup, calibrating, testing, fine-tuning, design, slicing, troubleshooting... etc.
Do enjoy ya!

the never ending journey of repraper , can make a whole movie out of it     

Is the thermistor working?

I think that could be the problem. It doesn't know the temperature and keep the power going

Is your bed size setting correct during slicing ?

Congrats on the assembly. 

As for your heater bed issue, it could be a few things but I don't know you will have the tools to test the system. Anyway you should read this http://forums.reprap.org/read.php?219,169361,169361 since this has the same issue as your heater bed transistor overheating. You have to check the resistance in your heater bed to find the current draw for a 12 volt supply. I have a 8" x 8" MK2A heater bed and it has a resistance of about 1 to 2 ohms which means it will draw about 6 to 12 Amps, so your bed should be between these resistance ranges. Another thing to look for are the polyfuse, which are the flat light brown pieces (either shape as a disc or square) mounted next to the transistor. Make sure the plastic bit that got burnt isn't the fuse because the fuse may not work properly when damaged. If all else fails, it could be the transistor and you may have to try replacing it with a different one.
Try checking your heater bed connection and measure the resistance of the heater bed.

No worries, you will eventually learn the terms and components while tinkering with your printer. 

That is bad, I mean that dark substance on top the heater block indicates PLA leakage. This is usually due to the heater block coming loose when heated or the threading may have been compromised. One way to fix this is to tighten the connection between heater block and heat sink by using a spanner. Make sure to heat up the hotend to about 100 to 150 deg before attempting to unscrew or tighten the  connection because the PLA inside the hot end will make it difficult to unscrew or tighten. By the way, that should be a E3D hotend right?

Hi, eehtsitna don't mention it ("Sorry").
You got the right attitude to ask and learn.
altan are right too for the instruction.
You can search online for the detailed assembly guide to tighten the heater block.

For example:
http://wiki.e3d-online.com/index.php?title=E3D-v6_Assembly

Appreciate the acknowledgement.  I am also learning from you guys as well.

Normally I would look up in reprap.org for the names of the things or the terms but forums are still the best place to ask.

If for some reason the tightening fails, use one or two layers of PTFE/teflon tape or plumbers white tape to form a nice seal between the hole and thread.  You can buy it off from any hardware store for a few ringgit.