Carolyn,
A few things to think about.
1. Be sure to drive any new-to-you rig for at least 1/2 an hour; pull over to the curb; pull into a gas station; park in a regular parking spot in a crowded lot. If you haven't hit anything, or scraped the air conditioning unit off the roof, you are good to go. Go through the motions on every single move you would make using a truck camper including sitting on the pot; using the shower wand (interior and exterior); seating arrangement for gathering around the dinette for a meal or schooling; sleeping arrangements for each regular occupant; lighting the hot water heater; selecting the correct fridge setting (12vDC; 120vAC; propane);where do the pots and pans go; drop and inspect the spare tire; pull down and pull up the stairs; where do you add propane?; where do you store everything you anticipate taking?
2. The Lance 990 is only for a long bed. Just know that a true 4-door truck with an 8 foot bed can be 22-24 feet long, too long for a standard car parking lot.
3. The longer your trip or living experience happens to be, the larger and more fully equipped you want it.
4. Look around for a buy on a truck and camper combo that is already assembled. There are many old timers getting out of the TC business and don't need the truck either. I live in No Cal and see the combos for sale all the time.
5. If you buy PP used, take a TC or RV guru along with you to inspect the rig and help you negotiate a lower price.
6. It's almost impossible to buy 'too much truck' when looking at any but the lightest camper. Dual rear wheels are more security but those 'hips' are tougher to wrangle when parking in tight quarters. For most people there is a 'period of adjustment'
7. It's easy to buy 'too much camper' for the truck, any truck.
8. If you plan on a moderate or lower amount of yearly mileage, a gas engine would be fine. If you plan on driving the TC more than 150K miles, total, then a diesel will finally payoff for the long haul.
9. Get your 'mirror technique' up to snuff.
just some things to think about.
jefe
Here is our 19 year old Lance Lite 165-s, short bed, bare bones, off-road equipped, 1842 pounds wet camper last week in Death Valley. It is just fine for TWO people once you learn the, "TC ballet" passing anyone in the aisle way. It's the shortest/lightest/least tall camper that Lance made at the time. The rig is 20 feet long and parks in any parking place. I include this as a foil on the other end of the TC scale.