I brought my bike to the bike shop today, because the rear wheel was having trouble turning without difficulty. I asked them to do a tune up and he looked at the rear wheel and said it needed to be trued and he would do that. He then called me and told me it needed a new rear wheel because there was a hole in the wheel and there were other places on the wheel where it was having tiny cracks. I had him put a new wheel on. He also explained to me that I was going to need new chain and also the rear and front gears are worn down. Is replacing the drivetrain on a bicycle normal wear and tear?

Yes..

Yes, but it usually takes a few thousand miles.

I generally replace mine annually, in the spring; snow, sand & salt are rough on the drivetrain.

Replacing the chain and rear gears is common. Replacing the front chainrings is less common.

Yes, chains and cssettes can wear fairly quickly, meaning a few thousand miles. OTOH, except for mtn bikes used in harsh conditions, chainrings last for 10s of thousands of miles.

i have inexpensive bicycles and still keep this up. where i am sugar sand is everywhere and normally change the chain each year depending on what bicycle gets used the most. i now keep a stock of at least 3- 8 speed chains, 1- 7 speed freewheel, and some plastic pulleys for the rear derailleur.

thank-you for your responses. I feel better about having to make these changes knowing they are normal wear and tear.

I am glad I read this. I asked sort of the same question in bike mechanics.
I have a raleigh MTB I want to refurbish. I bought it 20 years ago. I want to refurbish both because of nostalgia, and because it fits me really well. The LBS said if I want a 'modern' wheel ( I am thinking of rhyno lyte) then I need new gears, shifters, chainring and chain. But if this is just normal maintenence anyway, I dont mind to spend the bucks and fix it up and pretend like Im 20 again. Its fire engine red, and I rode it until everything wore out--no maintenence at all

Would think that you just need an 8 or 9spd cassette, matching chain, and shifter for the rear. Front shifter to match is optional.
I like the rhyno lites just fine. Super sturdy, old school rim. So is the CR18, and a bit lighter/cheaper.
Alex Adventurers are also just fine, easy to find, affordable.
Velocity Aeroheats are great all rounders in the 26 inch size.
I try to stick with 36 spokes in the rear.