It is very easy to change a GPU. First make sure your GPU will work.
Hi-end GPUs are PCIE-x16. Most Dell computer are only PCIE.
Do your research on the card and make sure your motherboard will support it.
Also make sure your OS will support the drivers.
Check out the link! It will tell you everything you need to know on how to install it.
http://www.wikihow.com/Install-a-Graphics-Card
Another important thing to keep in mind is the PSU.
Most Dell computer come with small 250 watt PSUs. If your using a low end card that is fine.
Hi end cards pull a ton of power. At minum you will need a 400 watt PSU.
Do NOT take it to someone unless you have no idea how to do it.
They will charge you way to much for such a simple job.
Happy computing!
