1984 6.2L Diesel K20 chevy silverado

Hey everyone! I know a buddy selling this truck and was thinking about buying it but I'm just wondering what ya'll thoughts are on it.
So its a 1984 K20 chevy silverado with a 6.2L Diesel,3 speed automatic, they put braand new tires, glow plugs and battery, Its got some body rust and rust holes here and there, what I believe is the power steering is covered in black gunk so I'm thinking its leaking, Same black gunk underneath the oil pan and a little next to the Oil dipstick, Otherwise the engine and tranny look okay, oil and tranny fluid is okay, Leafsprings had some surface rust and I dident see anything alarming with the frame.
The truck reads 45 thousand miles on the odo but for the condition of the truck it seems like the odo may have rolled over once? so 145 thousand miles? The owner said it ran good but the starter went out and its all it needs assuming everything else is still okay, but it doesent run of course because of the starter, and that's only but about $200 to fix, I've never fixed a diesel before nor really a gas engine, I don't really have any specific questions other then your guy's thoughts and opinions of buying it and turning it into long term daily truck, and especially me being only but a motivated backyard mechanic! Any tips or suggestions would be greatly appreciated to, I want to buy it but just dont want to end up regretting it in the long run! Thanks!
Edit: I do believe that last picture is the Power steering gear box, and thats $350. Its black gunk but I'm not 100% sure if it even leaked or might be coming from somewhere else!
Edit 2: My one buddy said that the 6.2L Diesel engines are really bad, they have starter problems and crack problems, gutless engines, Blows head gasket past 100K miles, etc, He said its a nice truck but it'd be best to swap the 6.2L for a 350 or 400 small block, or a 454 big block, and if I wanted a diesel to go for a Cummins, What's yall thoughts on that? Thanks!

Personally i love the 6.2 for what it is...
Cheap to run,parts are cheap,gets great fuel mileage,easy to work on,reliable if you remember what they were designed for.
That said i have hauled huge weight with mine,talking 30MPH going up hill,and i had no issues because i drive it as it was designed.
I don't expect it to maintain legal highway speeds when loaded,but i know that when i leave home with it there is a very slim chance that i will be stranded by it.
Simple to work on with average tools,so fixing on the side of the road is doable.I know of one truck in town here that has a tired old 6.2 in it that will not die,the present owner does nothing for it except drive it.It is heading towards 300 K miles with the original motor.The truck has been local all its life.