Without actually seeing your item , I'd guess that the price the Conservator quoted you is really 'in the ballpark' for the kind of work needed to bring the item 'back' to it's original "pre-cleaned" condition/patina .
Every professional Conservator I've dealt with , over several decades , use a 'standardized' set of tables to calculate the area ( of whatever material ) in need of conservation &/or restoration , in regards to price of each service they provide - it does not matter if it's a Van Gogh or a crayon drawing from a kindergardener .
It's usually calculated in square inches ( sometimes in square centimeters too ) , and sometimes prices will vary a bit , between Art Conservators in the same region .
In light of the fact that that restoration , as well as conservation , are services that might be needed for your total item (approx. 450 square inches) , that's less than a buck per square inch .
You could , of course , purchase books and study the processes you'd need to know about for a few years . Purchasing the tools and materials for actually performing the work , you could then buy some cheapo items to practice your new skills upon in the ensuing years (prior to attempting work on the item in question) .
I've studied a few processes for specific types of artwork myself , and where I don't feel competent enough , I just call in the 'Pros from Dover' .
In my early years of 'antiqueing' I've goofed-up in many ways that I don't today , and I now consider my many errors as real "learning opportunities" that have great value to me now .
That's my 2 centavos worth .
Welcome to the forum , edweather .
