Here's how we do it: Each year we forecast/plan our infrequent but expected expenses. These are things like saving up for a new (to us) minivan, car insurance, HOA dues, Christmas, saving up for vacation, new cabinets for the school room, etc. Based on those expenses, we automatically transfer $xxx each month into our "short term savings" account. Then, during the year, as expenses come out, we draw the money out of the short-term savings account.
We've found many times that over the course of the year, our priorities change, so we make adjustments. For example, we had budged several hundred dollars to rebuild our deck. But over the course of the year, that project became a lower priority, so we reallocated those funds to other things, like buying me a new suit for church, installing pantry shelves, etc.
In your case, it sounds like you're hesitant to spend a huge chunk of money. I know the feeling. But if it's something that's you feel is worth it, and you've got the funds for it, and you're not jeopardizing other goals, then QUIT STALLING AND DO IT ALREADY!