I have a 2000 Toyota Avalon with about 85,000 miles on it; tires have never been changed. Winter's coming up (I moved to Denver 2 years ago from LA...winters are bad here) and I admit I'm not knowligable when it comes to cars, but I just did the penny check on them. The 2 back tires are fine, but the front tires are bald... so when I get my tires changed, do I just change the front two or all four? Also, how long does the process take, and about how much can I expect to pay?

Change all! Looks like it will be a cold wet winter, if not you still have the comfort of having new. You will want good tires, probably 75-125 each, 1-2hr at most, if you are good at a little bit of research do that then hit Sam's club, watch some of the tire stores they may hit you for other repairs while doing the tires.

Generally, on tire changing, it takes between 15-25 minutes per tire, depending on the profile and rim design, thats also including balancing. Since you have never changed the tires on the vehicle, I would suggest changing all 4 tires as with age the rubber dries out and starts to crack and is more likly to blow out (although very rare on weather cracked tires). Going into winter its always good to have good tires on your car. Since you are probably inexperianced in driving in icy/snowy conditions I would recomend snow tires (they do not act like an all season or summer tire on dry road, but they will be a lot better then an all season or summer tire (summer tires in ice and snow is suicide)). For a good quality tire, I would be guessing starting at about $100 for a decent quality tire, plue installation, (at my shop about $20/tire). If your rim size is an odd or uncommon size, tire prices can go up to starting at $300+. I would expect to pay between $120-$180/tire with installation for a good quality brand name tire. Assuming its a relativly common size.

I have seen some tires starting at $60, in a brand name tire, but leading into the $200 - $300 range for the same tire in a different odd ball size.

Never been changed? I'd suggest all four and get all terrain tires since you live in Denver. They are a lot better on snow and ice.

Depending on the qrade, brand, quality of tires you get you'll be paying anywhere from around 265.00 to 500.00 for four new tires. That includes mounting them and balancing them.

Expect to spend anywhere from a hour up depending on how busy they are.
I usually try to hit them first thing in the morning before they get busy so I can get in and get out fast.

I would buy Four new ones because you will be able to get the best traction. It takes the tire place an average of 90-120 minutes to change the tires on a car. To know how much it will cost, you need to know if you are getting expensive or cheep tires. The cheap on will maybe only last you about 40000 miles while the expensive ones may get you to 90000 miles. In my opinion, I would go for the more expensive ones. cheap tires cost around $60 a tire while the expensive cost around $90. I bought Goodyear Eagle Response Edge tire for $120 a year ago and they have been great. Buy tires that are discontinued or are last years model because you can get them cheaper and they work just as well. Avoid Kelly tires all together because I have a friend that had a severe blow-out with one when it was 2-months old, he contacted Kelly Tires and sent them the tire, they said it was bad rubber.

How okay are the back tires? It is your call. You can either save money and risk it, or buy the tires, and have piece of mind. The more tread you have on your tires, the more control you will have on the road, but who knows if you even need the extra traction.

If you're not low on cash, then I suggest buying 4 new tires because 85,000 miles on 1 set of tires is crazy! haha, usually tires wear out around 40,000. You must be one safe driver. On the other hand, if you are on a budget, it is completely fine to just buy 2 tires.

The process takes 30 minutes if there's no wait.

You can expect to pay $50 up to $200 for each tire, plus mounting, tire disposal, valve stem and warrenty if there is any.

all four would be best. since your front tires give your your traction ans most of your braking and steering, these first if you have to make a choice. The back ones will help prevent spinouts if they were fresh. Get either good all-season tires if you don't drive a lot or long distances, if you have to rely on your car or drive a lot, then get tires that are M&S (mud and snow) or winter radials. (They don't make "all-terrain" tires for Avalons) Price shouldn't be more than $100 per tire (installed) expect it to take an hour to remove the old and install the new. Also, a good idea to get an allignment to protect your new tire investment. Some garages will offer a discount if you get the tires there too.