New Battery

My main lap-top computer needs a new battery (well it has been in daily use for the last 10 years....) and, having replaced batteries and increased memory on a number of devices in the past, I thought I'll buy a replacement battery and get the job done.
Amazon delivered the battery and I got on to YouTube to watch a tutorial on how to proceed.  I soon realised that I was being far too optimistic thinking I was going to do this myself ..... it's a very complicated task and rather beyond me.  I'll have to sublet the job to a professional .... it's the safest way .....