Sure. Weight work is a must. Example-I was the fastest in my life just after my army. That was the best shape i have ever reached. Food, resting/sleep and hard training with surgical precision. Comparing to those days, now i am more like a grandma
Regarding your question about workout my advise would be-find the best way, your way, size and scope and type of training. Best quidelines you may find on interenet, of course.
I used I and I still use strength factor training (divide total weight with minutes and you will get factor: pounds/minute or ks/minute. for example if you can push and pull 6t in 60 minutes then your factor is 100 kg/min). High intensity, no more than 60 minutes.
Adding weights is definately a good idea. Working on my core, doing deadlifts, etc has completely changed my mountain biking. I have much better balance, feel alot healthier, and alot more in control of my bike. Also helps if you need to bail alot - good balance = landing on your feet and not landing on your face (most of the time)