Two months after I bought it my oil pump died and made a hazard in the whole engine. This was probably because the previous owner didn't took care about the car.
I changed all four pistons, oil and water pump.
Year after I had loads of trouble with electronics. The main fuse box got rusted, also most of the connectors on the side marker lights and back lights. I changed the main fuse box and cleaned the connectors.
Few months the main commutator died. The solution was - change the commutator.
Also the most problematic thing about 1991 Samara was the fuel pump. In 3 year period I swapped four fuel pumps, of which one lasted only two months. Beside having two fuel filters (one regular and one conditioner) the dirt managed to damage Samara original pump. The solution was - I inserted Lada Riva fuel pump which now works perfectly.
The most touchy thing is the carburetor. If the dirt somehow passes both filters and fuel pump (specially if the pump valves are damaged) there is no doubt that the carburetor will start acting strange. The carburetor is probably the most problematic part in the whole engine. It should be cleaned from time to time - regularly.
The chassis is well built and strong, however, it lacks protection on few places. Specially on the rear side skirts (sometimes on front sides kirts), on the bottom sides of the car and on the rear door. Mine rusted on the trunk door, left side skirt and left door, which I fixed for a bargain.
My Samara has original metallic paint, which isn't like the other regular oily paints. This color didn't fade, and didn't loose it's shine. However, the regular paints, if the car is left on the sunshine/rain/winter will fade and loose it's gloss. Be sure to wax it from time to time.
Interior is quite spacious and has a lot of space. Specially on the front passenger seat and on the back seats. There is place for head for all the passengers and in some Samara there are seat belts on all seats.
Seats are comfortable, but if you haven't got seat cover be sure that seats will be teared after few years of intense driving.
Commands and dashboard are all on logical places and can be seen very good (wheel doesn't cover any part of dashboard). However the dashboard sometimes reflects on the windshield glass which is not for a praise.
The dashboard is made out of cheap plastic and if you don't spray it with high quality dashboard spray it is doomed to crack on the sunshine. I will also loose it's color. So, take good care for the dashboard.
Interior heating and cooling system - heating is excellent, especially if winter is very heavy at your places. I never got cold in my Samara. Interior gets up to wanted temperature in a matter of minutes (3-5 minutes). Because of good heating, the cabin cooling system is poor and the ventilator that pushes the air isn't quite strong. Anyway, all opened front windows will probably solve your problem.