A few things to think about.
1 Get the pond as big or bigger that you think you will ever need
once a liner is installed you cannot make it any bigger.

2. Yes you can install the liner yourself. you will need sone help. You just need to be strong to install a liner not smart.(I CAN SAY THAT BECAUSE I DO IT )

3 A trench will need to be dug around the top of the waterline the liner folded into the trench and is covered. This trench can be 2 feet deep,and will hold the liner in place .

4 Cover the liner with a min. of 1 foot of dirt, this will hold the liner down, protect it from animals and also the sun.

5 Be carefull not to let any rocks or sticks puncture the liner from on top or the bottom. In rocky soil a felt liner to protect the plastic is cheep and worth the money.

6 Get all the water to drain into the pond at the same place and fix this place so the water will not wash the dirt off the liner. Rocks, more liner,old tin.

OTTO