Babylove, welcome to the forum.
As you have read up to this point, there is a lot of information needed to make sight-unseen recommendations.
Unless your decision to replace the engine is based on a professional decision, I wouldn't be in a rush to switch it out.
In my opinion anyway, the easiest method of telling whether an old engine is worth fixing or switching is a cylinder compression test.
The end result of that test can be a huge deciding factor and may save you a bundle of money.
While I am aware cost is almost Always a definite factor in this endeavor, installing a used engine is always a gamble.
Just be careful and don't rush the process and make sure you do your 'homework'.
