First, if this is your first gun and you have never played here before, get the TM one. The TM Hi-Capa's are excellent guns and you can find a huge sticky on them that covers pretty much everything you would need to know about it. Used frequently doesnt always mean abused. I use my TM Hi Capa all the time because i love it. Why spend an extra $80-90 on your first gun? If you liked the Hi-Cap in HK then stick with it here. Try out the TM. Depending on the brand of mag they might not be compatible with the WE one.
You dont NEED an AEG, however if your playing outdoors it is highly recommenced as they have a much longer range and are much more accurate. If your playing indoors then you can sport just a pistol depending on the type of game your playing. Their is nothing wrong with running just a pistol, as i have on numerous occasions.