Help Please help with passage translation

Aisatsu!
Been a while, hope someone can help me with a little something.

The following is a piece from Hagakure by Tsunetomo Yamamoto [ kodansha, 葉隠（上), p. 370, chapter 63]

知行のご加増や、金銀を過分に拝領する時ほどありがたいことはないけれども、それよりむしろ、おかけいただくただ一言がありがたく、その忝なさに腹をも切る志が沸き起こるものである。
Chigyō no go kazō ya, kingin ｗo kabun ni hairyō suru toki hodo arigatai koto wa naikeredomo, sore yori mushiro, okake itadaku tada hitokoto ga arigataku, sono katajikenasa ni hara ｗo mo kiru kokorozashi ga wakiokoru monodearu.

The passage in question is the blue highlighted, chigyō no gokazō ya.
I am certain that the gist of this text is that putting aside the accumulated wealth, just a word of gratitude induces the writer with such a shame of gratitude that he actually feels like cutting his stomach... Yes because that what japanese ex-samurai turning into monks back then did.
Maybe if we would leave the first part out, the meaning would be probably the same, but that is why I look for consultation.

The writer is suggesting examples of two things that make people happy, such as

知行のご加増や、金銀を過分に拝領する
Getting an increase in stipend, or receiving a more than expected amount (bonus) from your Master/Lord

Fearabhata said:

I am certain that the gist of this text is that putting aside the accumulated wealth, just a word of gratitude induces the writer with such a shame of gratitude that he actually feels like cutting his stomach

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Sorry to point this out, but your interpretation is way off.
～けれども、それよりむしろ is not "putting aside". It means that 知行のご加増や、金銀を過分に拝領する時 are most grateful, but rather, おかけいただくただ一言 is more grateful than those things. Notice that おかけいただくただ一言がありがたく means "just a word given by your Lord is grateful", not "just a word of gratitude". (Incidentally, "just a word of gratitude" is ただのありがたい一言.)
Also, 忝なさ doesn't have a nuance of "a shame of gratitude" at all. He says that おかけいただくただ一言 is much grateful, and a will as if you can even cut your stomach arises by the gratefulness of it.

Fearabhata said:

Aisatsu!

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Unlike "greetings!" in English, あいさつ/aisatsu is never used as a word of greeting.

Toritoribe said:

Unlike "greetings!" in English, あいさつ/aisatsu is never used as a word of greeting.

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Not true. We have one example right here in this thread!

Eh, kuchimakase no yotabanashi :/
Always using it only when sitting at the counter, greeting the chefcook. Kanji-wise it says "drawing close", which is what I do, just adding a humouristic flavour to it. It is ok when it is not a formal setting. Sorry to hurt your feelings.

Although "aisatsu" is used wrongly, it's understandable enough what you wanted to say by it. My main point is "your interpretation is way off". Furthermore, the more important problem is that you thought you were certain you got the gist of the text. This can be a fatal defect of interpretation by yourself alone. My two cents.