30 years of paint buildup on my new condo walls!?

[damaged bad at best]

im 23, i just bought my first condo, and its kind of a fixer. 1100 sq ft. one of the big projects will be to paint throughout (for some reason, the previous owners thought it would be a good idea to paint all of the walls, doors, mouldings, and ceilings in blood red). the problem is that there is just SO MUCH paint buildup and they prepped very poorly. the walls have roller marks and roller fuzz stuck under paint, and there have been so many poorly done layers that the mouldings have now become one with the walls. i guess my question is how will i ever get my walls to look normal again? i have an electric hand sander i thought i might use to smooth down my walls but im not sure how. also, i am not opposed to replacing my base and crown mouldings, although once again i am not quite sure how.