After 5 years of non use, what precautions should I take before turning on a Commodore CBM 3016?

I've finally taken the jump into retrocomputing with something I've always wanted to own, a proper Commodore PET, or CBM 3016 to be exact!

The seller said 5 years ago when it was last turned on, that it worked perfectly fine. However I do wanna take some precautions before reawakening it. Not that something blows after all this time.

I however am still pretty new to retrocomputing and wanted to ask the experts on here, If/what I should first inspect under or over the hood before turning it on? Thanks in advance!