Since cooling is such an issue with this notebook, if you take the heat sink off of the processor and the graphics card, use fresh thermal paste and remove the old thermal paste on the two parts. It's that greyish residue on the chips. It's not unreasonably expensive and it can really help with cooling issues

You may want to look at a separate guide for applying and removing thermal paste, it's not entirely complicated but you don't want to make a mess of your work and need to redo it later

Hopefully once you put it all back together, your DV7 provides you with years of valuable service. Just remember not to over-tighten screws so that if you have to do it again, there's still enough thread to pull them out again!