Better do it yourself, that way you know what you have.
For me, it was a bit more. From the modules to the inverter room it was 25 m of cable length to the inverter room and from the meter to the inverter room then 35 m. The storage and inverter are housed in an outbuilding. Chiseling and shafts, laying protective conduits, etc.
I personally picked up the storage and only paid in cash upon handover. The modules were from a small local dealer and were then delivered directly from Baywa to me by freight. I paid a 1000 Euro deposit and the rest only after the Baywa delivery note was available.
I ordered the inverter online and paid via Paypal. Rails, holders, plugs, cables, etc. all online.
You have to be careful about what is deliverable. The storage must fit the inverter and you should also get a suitable smart meter. There are plenty of modules. Anyone who absolutely needs a Fronius inverter can only operate it with a BYD storage.
I now have the Huawei system and am more than satisfied with it. A year ago there was simply nothing else available. Still, I only managed with difficulty and without looking at the price to get one of the few available smart meters from Huawei. Others also fit poorly. So you should have a good plan.
Still, be careful, there are many fraudsters on the internet. I would not pay in advance to any dubious online shops. Goods against money. Period.
Whoever connects the system does not matter at all. From the meter onwards, anyone can do what they want. For me, an electrical specialist company did it. They set a residual current device before the system and sealed it. It was then supposed to be put into operation by the energy supplier. On the same evening I cut the seal and practically put the system into operation myself.
The meter change then took place sometime in November. A subcontractor from the energy regulation. Not a word about the active system. It would have cost me over 2000 kWh if I had waited for them. Some people wait over a year. Completely against the legal requirements.
Once again. After the meter I do what I want. Of course all within the scope of VDE regulations. After years of making everyone crazy about the 600 W of a balcony power plant, now it is possible to simply plug a plug into the socket and feed in.