Annapurna Base Camp is around 7 days trek marked as moderate to high. I visited this year April which was a good time to go. The trek has about 10-15 km daily with ascend of about 1000 m (there are some parts for decend as well). There are many adventure companies that provide packages as well. We went with a company called Bikat Adventures. Not the best experience. You can try with some more famous ones. Cost generally is around 22-30K per person depending on group size and discounts. You can also try the local vendors in Nepal which are cheaper.
You can look at some blogs for more details or ping me for anything specific you want to ask.
Yes I can answer you about Mount Everest you need to climb few mountains before attempting mount Everest mount Everest is costly deed 30 lkhs ruppes. I recommend you to watch some video bright side every thing to know about Mount Everest