any suggestions?

I have a 99 chevy express 2500 for a work van and I have a few questions. I replaced an alternator recently and afterwards when I start it up every so often the belt squeels for a few seconds and does it louder if the heats on. Is the belt not tight enough or too tight or what? Secondly the fuel pump got replaced a couple of months ago and about a week ago I noticed the needle on the fuel gauge is vibrating so rapidly it almost looks like its still unless you look closer and see that it is moving. And lastly the cruise control quit working on me on my way towards Kalamazoo. Does that run off of vaccuum hoses or what? Can I fix it myself? Any ideas would be greatly appreciated. Thanks!!!

I have a 99 chevy express 2500 for a work van and I have a few questions. I replaced an alternator recently and afterwards when I start it up every so often the belt squeels for a few seconds and does it louder if the heats on. Is the belt not tight enough or too tight or what? Secondly the fuel pump got replaced a couple of months ago and about a week ago I noticed the needle on the fuel gauge is vibrating so rapidly it almost looks like its still unless you look closer and see that it is moving. And lastly the cruise control quit working on me on my way towards Kalamazoo. Does that run off of vaccuum hoses or what? Can I fix it myself? Any ideas would be greatly appreciated. Thanks!!!
The belt could be loose but you can't adjust it, were the pullys on the alt the same size?

I'm sorry I can't help with the other items

Not sure about the pulleys, but when I put on the alternator I loosened the screw on where I thought the tension release should be but it wouldnt budge so it came right off. Then I put the belt back on and pulled it pretty snug and tightened it back up.