...putting a L67 in my 97 SSE?

Alot of money?
What would all have to be replaced?
Would it be worth it?

New transaxle, new computer.... what am i missing?

I would suggest reading the "Can I supercharge my SE or SSE?" article in the Techinfo, Specifications page. It answers alot of questions on this matter.

In Short to do this you will need at least the following items:
The L67 engine and drive train
The L67 computer and wiring harness
A new exhaust would be good
A new instrument cluster (or at least a SC boost gauge)
I would say you would almost need traction control if you don't have it. (because of the extra power) I might be wrong on this though. You might not need it but it would sure help.

Here is a link to the article I am talking about. If it was me I would do as it suggests and just see the 97' and buy a SSEi. Unless you have a L67 engine and drive train sitting around, It will probably about the same $ in the long run and you will have all the SSEi features like Traction Control, Digital Climate Control, HUD, etc.

http://www.bonnevilleclub.com/techinfo/?article=43

well my SSE has Traction Control, Digital Climate Control... etc

I just was thinking if I plan on keeping the car forever, the more life I'll get out of it with a heart transplant (and more HP...)

You will need to find a L67 engine, drive train, and computer then. Be careful were you get it. As one would expect the a lot of the SC engines have been used and abused. If you could find a bonneville that had some rear end damage with a good engine you would be in business. You should be able pull everything out of the damaged and place in yours make sure you change everything out. I.E. transmission, exhaust manifolds, wiring harness, and computer. Also the Buick Regal and GTP'* should have the same engine in them also I believe there are some SC Park Avenues out there also if you wanted to broaden you search.

You are probably looking at about $2500 to $3000 to find what you need plus you would still have to install it.