Header tank easily replaced?

Hi I've been in hospital for 5 months and in my absence my header tank has stated to leak between the seal of the header unit. Not the seal between the header tank and the boiler but where the header tank has been welded together. I know the leak is there as I've watched the water bead up and drip down.

I've checked online and there's a replacement for it but was wondering if it's a a simple job of unconnecting, removing the tank and connecting again? or is it more complicated? I only ask because my brother in law is quite handy as he's a builder and general jack of all trades.

Any Advice will be greatly appreciated. Thanks.