What size motor does the escalade have? It should have a timing chain (not a belt). Chains usually don't have a change interval specified. Often they break only if a guide breaks. Sometime the tensioner will get loose and cause a running problem. if this happens and you end up changing a tensioner then you could change the chain as well (and any guides).
This is quite a complex operation. Setting up a new computer requires specialized (and pricey) tools. It's certainly not worth buying the tools to do this (unless you are a mechanic and going to be using those tools on multiple cars). I'd recommend you bring this to a shop.
Check out the service schedule on this page. For your car there is only one thing to check at 50K. So the cost should be minimal. It appears the next major service is at 72K. You can also use the pre-service section of our site to estimate costs for certain jobs.