Well a compression test itself is only a time based charge. An hour (two maximum) would be about right depending on how versed the mechanic is with the engine. So thats definitely worth doing. As for what it reveals then thats another story.
If all the compressions come back equal and within range then its probably worth re-examining the breather system replacement.
If it comes back to reveal a the cylinder/s are showing signs of wear then there are temporary fixes using various "'wonder sealing compounds" none of them work on a long term basis but they can tide you over until you make a decision.
The rebuild, cause dependent, will not cost a huge amount in parts, its the labour cost and future reliability that is whats at risk here.
Depends on how attached you are to the car and what you will replace it with.
If the sale cost will be what you purchase another car with, you run the risk of picking up something that could have exactly the same issue, only you dont know about it.
If you are getting something newer and are just using the sale price to add to the funds then you should probably consider getting rid of it.
Hope this helps
All the best