Does CDN is good for seo and Which CDN is best

I am running a 15 months old pictures wordpress site and my website traffic is increasing so site loads slow because it put load on server so plz give suggestion that i have to upgrade server or use CDN?
1: Which CDN is best for indian traffic website?
2: Can we use CDN with already running website?
3: If i use CDN with already running website then image path and links will change to CDN different IP,s paths so my site will get many 404 errors and link problems so instead of good seo and more traffic it will put negative effect on traffic and seo, so what is the solution for it?

I will be very thankfull for your help.

Not if you do things properly. It might take a bit of effort to update all the links to the CDN, but you can do it. However, my first question would be about how well optimized your images are.

A CDN doesn’t help with SEO.

All it does is shift the load of downloadable content (images, videos, documents, etc) to an external server.