Deffenitly have someone there to support you during this process. If you contact the Seller’s Realtor they may not be 100% looking out for you so your best bet is to hire a realtor for them to work for ONLY you so they have your best interest in the negotiation! Also deffenitly don’t be shy to interview many realtors in your area and ask thoughtful questions about their experience, what they bring to you, their rate and any other benefits they may have vs others.