A good buyer agent has plenty of people he or she has worked with that you can talk to for reference. If they don't, keep looking! A good agent is looking to stay in business for a long time, not just make a quick commission. That is a lot easier when you have left a trail of happy cutomers who gladly refer you more business via friends and family. Also a good buyer's agent will criticize,as well as praise a home, and it's features. A bad buyer's agent never says anything negative because they don't want to get in the way of you making an offer. Pay attention to that!
Your Realtor can show you what the current average market sale price to list price ratio is, and that can be very helpful in determining your most aggresive list price. The best and first course of action is to make sure you have a current and thorough market analysis done by your Realtor, because a bank appraiser for any subsequent buyer mortgage will be looking at the same information. The sale price has to make sense to the appraiser, and if you have data to support the right price, the house will appraise. Get a feel for where your house fits into that market analysis report, and price it so it stands out as the best overall value among the similar homes for sale in the area.
Yes you can, but as a practical matter it is not nearly as easy to sell a home with a tenant in place than it is wthout, for so many reasons. Tenants, even good tenants, can be an obstacle to showing & selling. So, if selling your home is your ultimate goal, you would want to make the path to the closing table as clear as possible. Decide which way you want to proceed and get a great Realtor!