I will offer up a non-specific alternative view on you rebuilding an engine. Meant in an respectful manner with regard to all alternate opinions (things really can be very difficult).
For a long, long time, people have told me I should not try to rebuild or fix something or ride a motorcycle or take a different job or whatever. I just don't have the "experience" (and sometimes equipment).
Well, do you know what I have? Ability, aspiration and persistence. The combination of these attributes leads to accomplishments, and these successes can never be taken away from me.
I do not know why anyone does this sort of discouragement (and this is not specific; it is very, very common; probably I do it too). After all, they, all of them, had once not done what they are telling you not to do, but now they have (if they have not done it, ignore them completely, probably in all things).
So, for a very specific, real-world example. I was told for years (decades, really) that mere mortals can not and should not rebuild an automatic transmission. So what did I recently do? I rebuilt an automatic transmission. It took me a long time and I had to buy a bunch of tools (and the best manuals and videos I could find). But you know what, I get to keep the tools for next time and the accomplishment stays with me forever. And as a bonus, I got to put the labor $ budget in to vastly superior parts. And the transmission works great. (It is in an F350, so those transmissions have to be right or really bad things happen).
Anyway, do you know how I know I can do these things that others tell me I can not do (this is very, very important)? BECAUSE SOME OTHER HUMAN BEINGS HAS DONE IT BEFORE.
Please don't let people hold you back from what you want to do.
Good luck to all.