Overload springs are always a good idea for stability and safety with extra loads.
Also, if the trailer hitch you had installed is a reciever type (or if a welded on type, can have a 2"box reciever welded on) A weight distribution hitch setup would help with stability and handling.
It's one of those setups you see on the larger travel trailers usually that has the two metal bars with chains that when preloaded, transfer some of the weight to the front of the vehicle and the tension helps keep the trailer from trying to change lanes on you everytime a big truck goes by.

If you go with one of those , do your homework and see what is available in different weight ranges( don't let some hitch shop sell you what they have onthe shelf if it's for a 10,000lb trailer. you only need a light duty one. there are a number of sites on the web to research).You don't want to get one that is rated for too heavy a trailer or the spring bars will be too stiff and when you try to tensin them it will pop the trailer tounge up too high and get squirrilly.
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-------Robert, '93 940t, '90 240 wagon, '84 240 diesel (she's sick) , '80 245 diesel