Do I need an architect or an interior decorator?

since you're not planning on moving any walls, decorator would be the right place to start.

I would say -

1.) If the work is non structural
2.) If the work does not touch plumbing stacks
3.) If the work does not touch the gas risers
4.) If the electrical work only includes the moving or addition of some wiring, but not any changes to you main box
5.) If the board in your building will approve these changes as only 'decorative' (i.e. non structural in nature)

Then you are okay to go forward with an interior designer.

many thanks...will the decorator/designer assist in sourcing electricians/cabinetmakers, etc..?

A designer should be fine. Just find one who does more than decorate. You need space planning and extremely minor changes that almost can't even be called renovation. A good designer should know sources and contractors who can provide what you need. But if you find an architect who is willing to take this on at comparable costs, that would be fine, too.

In terms of cabinetry - this is THE most expensive part of most renovations. The concern here is twofold - the contractor/cabinet maker that your interior designer/architect uses has to be terrific technically speaking. However, this has to be balanced against the quantitative cost, which will rise as the quality of work you request increases. Therefore - and I cannot stress enough - you must request to see the finished cabinet work of the contractor your interior designer/architect and you decide to use BEFORE committing - if you can, request to go to a couple of apartments locally that the contractor has done work in recently, and look VERY carefully. Not just the overall appearance - but at the mitered corners, the seams, the edges, the type of hardware used, the real detail nitty-gritty details. It's quite important.

I'd like to meet the decorator who doesn't suggest moving walls.