i am having some hopefully minor difficulties with my 2000 montero sport. when i drive, usually above 50 mph, i get a shaking on the front left tire. after speaking with some people i am confident it is the wheel bearings. i have read they can be replaced or retightened/greased. how do i know which of these needs done? how much time would be involved to do this myself? also, if i took it to a mechanic, what is a reasonable estimate? thanks in advance!

Its not a big job to do maybe 1.5hrs per side for a mechanic. I would do bot sides as if one is bad the other is going that way. If you have shaking because of the bearings most likely you will have to replace one or both which could cost some $$. Get a mechanic to check out first and give you some prices to go by. Any place that does wheel alignments would be the best as they work on front ends all the time.

Jim