Vauxhall vectra 03 petrol auto

Hi can anyone advise me of my problems, first problem is the revs, the revs do not seem to be right to me, when I Rev the car up and down as the revs go down the car vibrates and the dashboard lights flicker and then the car stalls, whenever I let the revs go down the car always seems to be on the point of stalling
Second problem is the auto gears the gears go up and down no problem until it goes into first gear, as it goes into first gear there is a thud threw out the car and when I'm stuck in traffic for a while the gears only go from second to fith and won't automaticaly change, even in manual I can only go from either fith to second
Anyone got any ideas what's the problem and a solution I realy don't want to take it to vauxhall and be ripped off buy them