Need Advice Regarding Replacing Motherboard And Cpu

I want to replace the motherboard/CPU of my desktop computer, as there are often problems that need to be fixed.

Currently, I have the following:
• Motherboard: MSI H61M-P21(B3)
• Processor: Intel Core i5-2400 Quad-Core Processor 3.1 GHz
• 2x 8GB RAM
• Graphics Card: NVIDIA GeForce GTX 260
• AVerMedia A323 MiniCard Hybrid ATSC (Used very occasionally)
• 3x internal 1TB HDDs
• DVD Drive

I use a laptop at work, but at home, I use the desktop for office work, mail, web browsing, photo and video editing (Photoshop and Premiere Pro). Windows 10 is the OS and I think Photoshop and Premiere Pro are the 2 programmes needing most memory. I do not play games. My video, picture and music collection is stored on a 1 TB drive. I only use one monitor.

A dealer suggested the following Core i5 8400 Pro Upgrade Kit (MSI B360M BAZOOKA USB 3.1 Motherboard + Intel 8th Gen Core i5 8400 Up to 4.0GHz CPU + 16GB DDR4 2666MHz RAM)

I have approximately USD500 to spend.

With the above in mind, what are possibilities that I can consider?