That might be a lot of work, definitely, but it is difficult to pinpoint it from here.
A smoking diesel means it gets too much oil, making the mixture too rich. The cause, from the easiest to the most difficult, can be a blocking of the air intake, a maladjusted or faulty injection pump or a broken oil scraper ring of a piston. If it is not one of the first, then it will be a big job, taking the engine apart.
About the hydraulics you will find a lot of comments here; check those for estimating what can be involved.
One remark: after such a long time standing it might very well be that all the greased joints have seized solid. If they are, you will have to take them off one by one and hammer them free. Mine is a 5745 that had been standing for 24 years and I had to do all of them but one, some even under a 50 tons
hydraulic press. Took me almost four days of heating and hammering through each micrometer of joint.
