Tried to start Xterra, wouldn't turn over, dash lights came on.

Sounds like maybe alternator problem allowing battery to go down where would not crank engine. Needs a lot more power to crank than turn on lights. Should have had signs of problem on charging gauge or idiot light. Check the battery connections also.

Your initial problem is battery voltage. There is not enough to power up the gauges and crank the starter. Why this is the case could be - a bad battery, faulty connections, corrosion build up, charging system failure. Start by getting a known good and fully charged battery into the Xterra. Then, have a starting and charging system diagnosis performed.