I'll be a monkey's uncle

Bob's your uncle

No problem, the solution is simple, there you have it, it's that easy, you have what you want, all will be well: indicates a desirable conclusion has been reached with ease.

I'll be

Expressing surprise.

I'll be bound

An expression of surprise.

I'll be damned

An expression of surprise.

I'll be danged

An expression of surprise.

I'll say

Used to indicate emphatic agreement

I'll tell you

Synonym of I can tell you.

say uncle

Synonym of cry uncle.