do I need to replace the motherboard

I bought a Asus AS-870-PRO Desktop PC in Apr 2011 and paid for extended warranty.
PC could no longer access internet in Dec 2012 - Network Adaptor need to be replaced.

Spoke with the PC repair technician engaged by the warranty company and was told that there are 2 options :
1) install a new network adaptor
or
1) replace the motherboard with a different model-the motherboard that come with my PC is no longer being manufactured

The technician's advice to me is to just "add the network card to minimise change"
The warranty company will call me today to go through the options.

I would be grateful if someone could advise me on which of the above options to take.
Many thanks in advance.
I have backed up my file using Acronis True Image.

Reasons that might force you to replace your motherboard are:

* CPU is not good enough for new games

* Motherboard is broken

* You don't have enough ram slots (Trying to come up with reasons)

* Not enough PCIe slots

* Doesn't not support sli

* Don't have the I/O you want

I think you should change your motherboard to a new one. The one which can work with all new processors and all new things. This gonna be better for you as it will help you to change other things too.

If you're motherboard or CPU is just malfunctioning, you can just do a straight swap by installing the same model. If you're looking to upgrade, though, you'll need to do a bit of research first.

you should replace you motherboard which is compatible with your new processor

Only required to replace your motherboard if either the motherboard is defective or broken, or when you need to upgrade to a CPU that's incompatible with that motherboard. If you're fine with your current motherboard/CPU then there's no reason to change it unless you're having issues with it.