Assuming you're using the stock CPU fan from the XPS?
The CPU is pushing 10 years old at this point and, assuming the XPS system was bought at launch of the XPS, it's right around 9 years old.
If you're using the stock fan, it's also ~9 years old then.......... '
So, yes. A replacement CPU Fan is, in all likelihood, a pretty good idea.
The Cryorig H7, Cooler Master 212 Evo and be quiet! Pure Rock are all $30-40 coolers, which might see a decent discount tomorrow.
The XPS cases don't have the best airflow either (generally only 1x intake or 1x exhaust) - so it might be worth considering a case replacement too.
Doesn't have to be anything fancy, but the XPS uses a standard mATX form factor and doesn't use proprietary PSU connectors.
Something more 'open' with room for additional fans may help too.
For example, you could transplant into something like this $20 case
PCPartPicker part list /
Price breakdown by merchant
Case: Rosewill - REDBONE U3 ATX Mid Tower Case ($19.99 @ Newegg)
Total: $19.99
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2017-11-23 14:32 EST-0500
The only (slight) headache that you'd need to deal with is establishing the front panel connectors layout..... as Dell uses a proprietary "all in one" solution. Not much too it, other than time.