Firstly hello to everyone and sorry for my not perfect english.
well story is, been working for auto electican for few years most of them are opel/vauxhall nearly expert on them,
so customer gets some unit like speedo, ecu etc from breakers and asks me to put in his car or swap with his unit all units are coded to car
code can be found in eeprom dump but not easy if you dont have pc programmer by hand. well got idea for standalone unit who can read code from it windows ce looks too complicated and harware isnt cheapes than i found Arduino dev bords, looks like they can do a job wiring and pcb's not a problem but when it comes to programming can do some things but looking at good tutorials.
If someone can point me to right direction or provide some code that would be great.
havent bought a dev board jet have seen some on ebay with lcd screen or can someone advice which is better
got some dumps from eeproms saved to test have attached image with place in dump where code is stored in case if needed
How do you access the unit's EEPROM (bus, soldering out)? You don't provide enough details to help you further. Provide links to all mentioned stuff.
OK will provide all steps what i do
- desolder eeprom from unit (some of them can be read in circuit but never tried can get corrupt data)
- using programmer read eeprom im using upa-usb
- find code in dump
- solder it back and than using diag tools reset unit and code it to car - this step can be done editing dump directly but it takes a time
so wanted to build unit what i can use anywhere and as small as possible
eeprom will be desoldered anyway from unit but if will be possible will try to implent direct dump editing (change bytes whats needed something like reset)
there will be few eeprom types but process are similar at the moment will stick at st 93c46 so8 package
link to datasheet http://www.st.com/st-web-ui/static/active/en/resource/technical/document/datasheet/DM00043901.pdf
dev board what was looking at http://www.ebay.co.uk/itm/SainSmart-Mega2560-3-2-TFT-LCD-Shield-Touch-Screen-SD-Reader-4-Arduino-UNO-UK-/280931953825?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item4168d96ca1
I don't know what a UPA-USB is. Do you have a link for that?
The EEPROM chip specifies a MICROWIRE bus but from the timing figures that seems to be an ordinary SPI bus. This means an Arduino should be able to read and reprogram these little chips. If that works in-place (without desoldering it) depends on the circuit it's used in.
Is the car code always at the same index? If not, do you have to search for it manually? How do you plan to get the replacement car code into the device? Using an Onscreen-Keyboard?
link to upa usb ELRASOFT Products
yes code is always in same places just changes according unit like radio has 93c46 code same place all the time, screen has same but can have 25c080 too code in different place.
looked at board with screen because before coding to new car old unit must be reset like droped to zeros its just a little changes in eeprom indexies, so plan is to make sd card with reset dumps and program them to eeprom or if possible change needed indexies directly in eeprom, screen would be used for unit selection radio, screen, ecu etc
Everything you write sound feasible and the Arduino Mega2560 with touch screen shield is a viable platform for your project. You just have to start it 
ok thanks for pointing to device wasnt sure if it will do a job will order it in few days
if i will need a help in coding is it ok to ask you for help?
Try beginning with the easy stuff and don't do the whole project in one task. Get familiar with the platform before trying to start with complex things. If you get stuck ask here in the forum for help but don't expect anyone here to do your job (we're happy to help but we don't make it for you).
Sure will start with something simple, never expected to do job in my place like i said in first post i can manage things but looking at tutorials have found one looks ok to start with code lenght bit too long but will use it as tutorial and will start writing own code for simple tasks like read eeprom
as guide will use this http://rweather.github.com/ardpicprog/programeeprom_sketch.html