The accelerometer measures the g-force (acceleration combined with earth gravity). If the sensor starts moving, it measures that. That is what an accelerometer does.

You should combine it with the gyro values. The gyro is not influenced by the linear acceleration. However, the gyro drifts, so the gyro needs the accelerometer as much as the accelerometer needs the gyro.
 

Earth gravity.

The accelerometer should have about 1g for the earth gravity.

You can safely connect everything together.
For extra safety you could add a usb hub between the laptop and the Arduino.

The ground clip of an oscilloscope is usually connected to the ground of the mains. Connect that ground clip to the GND of the Arduino. The laptop and the wall wart are not connected to the mains ground. So even if the ground clip of the oscilloscope is accidently connected to something else, there is still no problem.

I think you have to use avrdude (for the ATmega328 without 'p') with the bootloader for the Uno (ATmega328p with 'p').
You probably can't do it from within the Arduino IDE, because the signatures don't match.

After that you can use the Arduino IDE and upload the sketches as if it was a Uno (with ATmega328p with 'p').
The ATmega328p has a few more registers, so if the Arduino uses those, you are in trouble. But I'm using my ATmega328 (without 'p') as a Uno for a while and have not encountered a problem yet.

ADDED: Maybe I misunderstood the question. I thought you want to replace a ATmega328p (with 'p') with a ATmega328 (no 'p') and use is as a Arduino board. If you want to replace the ATmega328 with ATmega328p, there is no problem at all.

The SS has to be output, regardless of which pin you use for ChipSelect. That was what I ment in my previous post. That is what is happening in that initSPI() code. That is good, you don't have to set the SS pin as output yourself.

The begin() function has a third parameter for the ChipSelect. You could use the SS pin, but also another pin can be use for the ChipSelect.
If you don't use the third parameter, perhaps it defaults to pin 8 or so.

I have a Mega2560 with Ethernet Shield, and a Uno with ENC28J60 and ethercard. So I don't have your combination, but with the right ChipSelect it should work.

It seems to me a power and voltage level problem, not a library problem.

If you have a MPU-6050 breakout board with a voltage regulator on board, you should use 5V and not 3.3V.
You could try a I2C level shifter if you use the Arduino Uno or Mega.

Any servo should be seperately powered. You can not use the 5V pin of the Arduino for a servo. The start current for a servo could be 0.5A to 1A, that is far too much for an Arduino.

The are a number of problems with the X-tal for RTCs.
Your battery could be empty or the X-tal could be bad.

The chip uses very little current. It is able to keep the data in memory with a low voltage. However, running the X-tal to get the clock running requires a little more voltage.

If you have the ethercard library running with a Uno and a ENC28J60, you are no longer new to Arduino. It is something for advanced users.

The Mega (and Mega2560) use the SPI bus the same way, but you have to adapt the pin numbers for the Mega.
If a different ChipSelect is used, the SS pin of the Mega2560 has to be set as output, to make the SPI hardware working.

The function "xferSPI()" in "enc28j60.cpp" is the function to communicate with the chip. It uses the SPI hardware by direct register access.
The ChipSelect line is set with the begin() function (the third csPin parameter).
I think if you set that to the SS pin of the Mega, it should work.

Normally a sketch is upload with the (virtual) serial port via the use.

The ICSP header are 6 pins. They are used for example to program a bootloader. But also a sketch can be uploaded via those 6 pins. But is programmer is needed for that. The programmer can be a USBasp programmer from Ebay for a few euros/dollars or even another Arduion board.

http://www.openmusiclabs.com/learning/arduino/isp/

If you become an advanced user of Arduino, as some point you might want to use that.

You fried the board. It could be the power circuit or the ATmega2560 itself.

I can think of one more test, but you need a programmer.
With a programmer and the ICSP header, you could try to connect to the ATmega2560.

You can't use a voltage divider to power something (you can, but don't do that).
You need a voltage regulator (7809 or LM317) or a DC-DC converter.

No problem at all.

The SD library
http://arduino.cc/en/Reference/SD
has only the read() function to read data from a file
http://arduino.cc/en/Reference/FileRead

I suggest to read a line (ended by '.' or '\r' or '\n' or end of file) in a buffer and use sscanf to convert the line into variables.

I used 9v transistor radio battery .I think it provides enough current, should i replace it with any high current rating battery??

Yes.

You need an electronic spring scale.
http://commons.wikimedia.org/wiki/Spring_scale

Google for pictures of : portable digital fish hook scale

But i don't know the technology inside of those. Perhaps a load cell ?