I'd change the spark plugs , air filter and do an oil change to start. Have them look at the tie rods and other steering pieces ,also the cv joints and front wheel bearings ,that bumps should be from one of those areas. Also look at the front stabilizer bar end links, could be that . The only regular problem with the 2000 model is a bad intake manifold gasket . It will cause a lean condition and run bad if that happens . The other thing that also causes a running problem is the distributor will go bad if the pvc valve isn't changed. Its cheap but the labor is a couple hrs to change the valve. Its cheaper than buying the distributor that can go bad if you don't. Good luck. We love our Altima . Its one of our 3 cars and just seems to need oil changes and tires ,little else.