Replacing my CPU

Hello. I am not sure whether this is the correct place to post it but I found it the most suitable. So here lies my question:

I have an Intel Duo 2140 (2x1.60GHz) and a Gigabyte 965P-S3 Mainboard. I want to get a new CPU i7-860 or i5-750 (Probably the i5 one) so can you please tell me will I need to buy a new mainboard and what kind (for i5 and for i7) and also will this new core + mainboard be able to run with my 2GB DDR2(it says DDR2 in Cpu-Z but I am pretty sure when I bought it that the garancy said DDR3) Ram and I also want to add 2 more GBs of ram (will it be possible?) and my Video card Palit GeForce GTS 250 1GB Ram.

Also when I buy a new CPU + Mainboard I would like to know if I will be able to move my old CPU (2x1.60Ghz) + mainboard to my old computer( I cannot tell you the details but I remember that its video card is GeForce 4 440 or something like this (the PC is from that time with 512 ram)). Thank you for your help and if you need details about my old PC just ask me - I will make sure to get them.

What sort of money are you looking to spend ?

bare minimum :-

CPU
Mobo
RAM

luxuries / extras

New Video Carn
New Case